Expandable intervertebral implant system and method

ABSTRACT

An intervertebral implant system for a human spine including a first body having a first external surface to be disposed adjacent a first vertebrae during use and a first internal surface opposite the first external surface, a second body having a second external surface to be disposed adjacent a second vertebrae during use and a second internal surface opposite the second external surface, an elongated insertion instrument releasable coupleable to the first or second body during use, and a spacer linearly advanced between the first internal surface of the first body and the first internal surface of the second body during use. The elongated insertion instrument guides at least a portion of the linear advancement of the spacer, and wherein the linear advancement of the spacer results in expansion of the intervertebral implant such that the first external surface and the second external surface move away from one another to expand a height of the implant.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.11/134,091 entitled “Method of Insertion of an Expandable IntervertebralImplant” to Charles R. Gordon, Corey T. Harbold, and Heather S. Hansonfiled on May 20, 2005 which is a continuation of U.S. patent applicationSer. No. 11/050,632 entitled “Functional Spinal Units” to Charles R.Gordon, Corey T. Harbold, and Heather S. Hanson, filed on Feb. 3, 2005.U.S. patent application Ser. No. 11/050,632 is a continuation in part ofU.S. patent application Ser. No. 10/634,950; U.S. patent applicationSer. No. 10/660,155; U.S. patent application Ser. No. 10/777,411; andPCT Application No. US2004/025090. PCT Application US2004/025090entitled “Artificial Spinal Unit Assemblies” to Charles Gordon and CoreyHarbold, filed on Aug. 4, 2004, claims the benefit of U.S. patentapplication Ser. No. 10/634,950; U.S. patent application Ser. No.10/660,155; and U.S. patent application Ser. No. 10/777,411. U.S. patentapplication Ser. No. 10/777,411 entitled “Artificial Spinal UnitAssemblies” to Charles Gordon and Corey Harbold, filed on Feb. 12, 2004,is a continuation in part of U.S. patent application Ser. No.10/634,950. U.S. patent application Ser. No. 10/660,155 entitled“Artificial Functional Spinal Unit Assemblies” to Charles Gordon andCorey Harbold, filed on Sep. 11, 2003, is a continuation in part of U.S.patent application Ser. No. 10/634,950. U.S. patent application Ser. No.10/634,950 entitled “Artificial Functional Spinal Unit Assemblies” toCharles Gordon and Corey Harbold was filed on Aug. 5, 2003. Each of theabove identified documents are hereby inforporated by reference.

BACKGROUND

1. Field of the Invention

Embodiments of the invention generally relate to functional spinalimplant assemblies for insertion into an intervertebral space betweenadjacent vertebrae of a human spine, and reconstruction of the posteriorelements to provide stability, flexibility, and proper biomechanicalmotion. More specifically, embodiments of the invention relate toartificial functional spinal units including an expandable artificialintervertebral implant that can be inserted via a posterior surgicalapproach and used in conjunction with one or more facet replacementdevices to approach an anatomically correct range of motion. Embodimentsof the invention may also be inserted via an anterior surgical approach.

2. Description of Related Art

The human spine is a complex mechanical structure including alternatingbony vertebrae and fibrocartilaginous discs that are connected by strongligaments and supported by musculature that extends from the skull tothe pelvis and provides axial support to the body. The intervertebraldiscs provide mechanical cushion between adjacent vertebral segments ofthe spinal column and generally include three basic components: thenucleus pulposus, the annulus fibrosis, and two vertebral end plates.The end plates are made of thin cartilage overlying a thin layer of hardcortical bone that attaches to the spongy, cancellous bone of thevertebral body. The annulus fibrosis forms the disc's perimeter and is atough outer ring that binds adjacent vertebrae together. The vertebraegenerally include a vertebral foramen bounded by the anterior vertebralbody and the neural arch, which consists of two pedicles and two laminaethat are united posteriorly. The spinous and transverse processesprotrude from the neural arch. The superior and inferior articularfacets lie at the root of the transverse process.

The human spine is a highly flexible structure capable of a high degreeof curvature and twist in nearly every direction. However, genetic ordevelopmental irregularities, trauma, chronic stress, and degenerativewear can result in spinal pathologies for which surgical interventionmay be necessary. In cases of deterioration, disease, or injury, aspinal disc may be removed from a human spine. A disc may become damagedor diseased, reducing intervertebral separation. Reduction of theintervertebral separation may reduce a height of the disc nucleus, whichmay cause the annulus to buckle in areas where the laminated plies areloosely bonded. As the overlapping laminated plies of the annulus beginto buckle and separate, circumferential or radial annular tears mayoccur. Such disruption to the natural intervertebral separation mayproduce pain, which may be alleviated by removal of the disc andmaintenance of the natural separation distance. In cases of chronic backpain resulting from a degenerated or herniated disc, removal of the discbecomes medically necessary.

In some cases, a damaged disc may be replaced with a disc prosthesisintended to duplicate the function of a natural spinal disc. U.S. Pat.No. 4,863,477 to Monson, which is incorporated herein by reference,discloses a resilient spinal disc prosthesis intended to replace theresilience of a natural human spinal disc. U.S. Pat. No. 5,192,326 toBao et al., which is incorporated herein by reference, describes aprosthetic nucleus for replacing just the nucleus portion of a humanspinal disc. U.S. Patent Application Publication No. 2005/0021144 toMalberg et al., which is incorporated herein by reference, describes anexpandable spinal implant.

In other cases, it may be desirable to fuse adjacent vertebrae of ahuman spine together after removal of a disc. This procedure isgenerally referred to as “intervertebral fusion” or “interbody fusion.”Intervertebral fusion has been accomplished with a variety of techniquesand instruments. It is generally known that the strongest intervertebralfusion is the interbody fusion (between the lumbar bodies), which may beaugmented by a posterior or facet fusion. In cases of intervertebralfusion, either structural bone or an interbody fusion cage filled withbone graft material (e.g., morselized bone) is placed within the spacewhere the spinal disc once resided. Multiple cages or bony grafts may beused within that space.

Cages of the prior art have been generally successful in promotingfusion and approximating proper disc height. Cages inserted from theposterior approach, however, are limited in size by the interval betweenthe nerve roots. Therefore, a fusion implant assembly that could beexpanded from within the intervertebral space could reduce potentialtrauma to the nerve roots and yet still allow restoration of disc spaceheight. It should be noted, however, that fusion limits overallflexibility of the spinal column and artificially constrains the naturalmotion of the patient. This constraint may cause collateral injury tothe patient's spine as additional stresses of motion, normally borne bythe now-fused joint, are transferred onto the nearby facet joints andintervertebral discs. Thus, an implant assembly that mimics thebiomechanical action of the natural disc cartilage, thereby permittingcontinued normal motion and stress distribution, would be advantageous.

A challenge of instrumenting a disc posteriorly is that a device largeenough to contact the end plates and slightly expand the space must beinserted through a limited space. This challenge is often furtherheightened by the presence of posterior osteophytes, which may cause“fish mouthing” of the posterior end plates and result in very limitedaccess to the disc. A further challenge in degenerative disc spaces isthe tendency of the disc space to assume a lenticular shape, whichrequires a relatively larger implant than often is easily introducedwithout causing trauma to the nerve roots. The size of rigid devicesthat may safely be introduced into the disc space is thereby limited.

The anterior approach poses significant challenges as well. Though thesurgeon may gain very wide access to the interbody space from theanterior approach, this approach has its own set of complications. Theretroperitoneal approach usually requires the assistance of a surgeonskilled in dealing with the visceral contents and the great vessels, andthe spine surgeon has extremely limited access to the nerve roots.Complications of the anterior approach that are approach-specificinclude retrograde ejaculation, ureteral injury, and great vesselinjury. Injury to the great vessels may result in massive blood loss,postoperative venous stasis, limb loss, and intraoperative death. Theanterior approach is more difficult in patients with significant obesityand may be virtually impossible in the face of previous retroperitonealsurgery.

Despite its difficulties, the anterior approach does allow for the wideexposure needed to place a large device. In accessing the spineanteriorly, one of the major structural ligaments, the anteriorlongitudinal ligament, must be completely divided. A large amount ofanterior annulus must also be removed along with the entire nucleus.Once these structures have been resected, the vertebral bodies are overdistracted in order to place the device within the disc and restore discspace height. Failure to adequately tension the posterior annulus andligaments increases the risk of device failure and migration. Yet in theprocess of placing these devices, the ligaments are overstretched whilethe devices are forced into the disc space under tension. This overdistraction can damage the ligaments and the nerve roots. The anteriordisc replacement devices currently available or in clinical trials maybe too large to be placed posteriorly, and may require over distractionduring insertion in order to allow the ligaments to hold them inposition.

SUMMARY

In some embodiments, provided is an intervertebral implant system for ahuman spine including a first body having a first external surface to bedisposed adjacent a first vertebrae during use and a first internalsurface opposite the first external surface, a second body having asecond external surface to be disposed adjacent a second vertebraeduring use and a second internal surface opposite the second externalsurface, an elongated insertion instrument releasable coupleable to thefirst or second body during use, and a spacer linearly advanced betweenthe first internal surface of the first body and the first internalsurface of the second body during use. The elongated insertioninstrument guides at least a portion of the linear advancement of thespacer, and wherein the linear advancement of the spacer results inexpansion of the intervertebral implant such that the first externalsurface and the second external surface move away from one another toexpand a height of the implant.

In some embodiments, provided is a method of implanting anintervertebral implant into a human spine including: disposing an upperbody into an intervertebral space between an upper vertebrae and a lowervertebrae, wherein the upper body includes a superior surface disposedadjacent the upper vertebrae and an inferior surface opposite thesuperior surface, disposing a lower body into the intervertebral spacebetween the upper vertebrae and the lower vertebrae, wherein the lowerbody includes an inferior surface disposed adjacent the lower vertebraeand a superior surface opposite the inferior surface, releasablycoupling an elongated insertion instrument to at least one of the upperbody and the lower body, and linearly advancing a spacer between theinferior surface of the upper body and the superior surface of the lowerbody. The elongated insertion instrument guides at least a portion oflinear advancement of the spacer, and wherein linear advancement of thespacer results in expansion of the intervertebral implant such that thesuperior surface of the upper member and the inferior surface of thelower member move away from one another to expand a height of theimplant.

In some embodiments, provided is an intervertebral implant system for ahuman spine including an upper body to be disposed in an intervertebralspace between an upper vertebrae and a lower vertebrae during use,wherein the upper body has a superior surface disposed adjacent theupper vertebrae and an inferior surface opposite the superior surface, alower body to be disposed into the intervertebral space between theupper vertebrae and the lower vertebrae during use, wherein the lowerbody has an inferior surface disposed adjacent the lower vertebrae and asuperior surface opposite the inferior surface, an elongated insertioninstrument to releasably coupled to at least one of the upper body andthe lower body during use, and a spacer to be linearly advanced betweenthe inferior surface of the upper body and the superior surface of thelower body during use. The elongated insertion instrument guides atleast a portion of linear advancement of the spacer, and wherein linearadvancement of the spacer results in expansion of the intervertebralimplant such that the superior surface of the upper member and theinferior surface of the lower member move away from one another toexpand a height of the implant.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will become apparent to thoseskilled in the art with the benefit of the following detaileddescription and upon reference to the accompanying drawings in which:

FIG. 1 depicts a top view of an embodiment of a cylindrical, expandableimplant.

FIG. 2A is a side cross-sectional view of the embodiment depicted inFIG. 1.

FIG. 2B is a side cross-sectional view of the implant embodimentdepicted in FIG. 1.

FIG. 3A is a cross-sectional view of an embodiment of an expandableimplant in extension.

FIG. 3B is a cross-sectional view of an embodiment of an expandableimplant in flexion.

FIG. 4A is a cross-sectional view of an embodiment of an expandableimplant prior to expansion.

FIG. 4B is a cross-sectional view of an embodiment of an expandableimplant following expansion.

FIG. 4C is a cross-sectional view of an embodiment of an expandableimplant employing buttress screws to secure the device betweenvertebrae.

FIG. 4D is a cross-sectional view of an embodiment of an expandableimplant employing an expansion plate with a securing keel to secure thedevice between vertebrae.

FIG. 4E is a side perspective of an embodiment of an expandable implantemploying a securing keel.

FIG. 5 is a side perspective view illustrating placement of anexpandable implant in an intervertebral space.

FIG. 6A depicts a top view of an embodiment of a c-shaped, expandableimplant.

FIG. 6B is a top view of an embodiment of a c-shaped expandable implant,illustrating insertion of expansion screws to expand the implant.

FIG. 6C is a top view of an embodiment of a c-shaped, expandableimplant, illustrating insertion of a non-threaded expansion member toexpand the implant.

FIG. 6D is a top view of an embodiment of a c-shaped, expandable implantwith a posteriorly positioned expansion opening.

FIG. 7A is a cross-sectional view of an embodiment of an expandable,articulating implant including an insert with stops.

FIG. 7B is a cross-sectional view of the embodiment depicted in FIG. 7Ashowing articulation of the implant.

FIG. 8A is a top view of an embodiment of a c-shaped, expandableimplant, illustrating the insertion of an expansion plate to expand theimplant.

FIG. 8B is a side cross-sectional view of an embodiment of a c-shaped,expandable implant, illustrating the insertion of an expansion plate toexpand the implant.

FIG. 8C is a side cross-sectional view of an embodiment of an expandableimplant, featuring stabilizers.

FIG. 8D is a side cross-sectional view of an embodiment of an expandableimplant in flexion, featuring stabilizers.

FIG. 9A is a top view of an embodiment of an expandable cage.

FIG. 9B is a side cross-sectional view of an embodiment of an expandablecage prior to expansion.

FIG. 9C is a side cross-sectional view of an embodiment of an expandablefollowing expansion.

FIG. 9D is a side cross-sectional view of an embodiment of an expandablecage with a larger upper surface area prior to expansion.

FIG. 9E is a side cross-sectional view of an embodiment of an expandablecage with a larger upper surface area following expansion.

FIG. 9F is a cross-sectional view of an embodiment of a cage that isexpandable in two directions.

FIG. 10A is a posterior view of an embodiment of a c-shaped lordoticexpandable implant.

FIG. 10B is a top view of an embodiment of a c-shaped lordoticexpandable implant.

FIG. 11A is a lateral view of an embodiment of a c-shaped lordoticexpandable implant prior to expansion.

FIG. 11B is a lateral view of an embodiment of a c-shaped lordoticexpandable implant following expansion.

FIG. 12A is a side cross-sectional view of an embodiment of anexpandable lordotic cage prior to expansion.

FIG. 12B is a side cross-sectional view of an embodiment of anexpandable lordotic cage following expansion.

FIG. 13A is a lateral view of an embodiment of a c-shaped lordoticexpandable implant with an inclined expansion member.

FIG. 13B is a side cross-sectional view of an embodiment of anexpandable lordotic cage with an inclined expansion member.

FIG. 14A is a perspective view of an embodiment of an expandable,articulating implant with a spiral cam.

FIG. 14B is a cross-sectional view of the implant embodiment depicted inFIG. 14A prior to expansion.

FIG. 14C is a cross-sectional view of the implant embodiment depicted inFIG. 14A following expansion.

FIG. 15A is a top view of an embodiment of a c-shaped expandable,articulating implant with a round insert.

FIG. 15B a side cross-sectional view of an embodiment of a c-shapedimplant with an expansion member/advancing element combination prior toexpansion.

FIG. 15C is a side cross-sectional view of an embodiment of a c-shapedimplant with an expansion member/advancing element combination followingexpansion.

FIG. 16A is a perspective view of an embodiment of an expandable,articulating implant before expansion.

FIG. 16B is a perspective view of an embodiment of an expandable,articulating implant following expansion.

FIG. 17 is a perspective view of an embodiment of a portion of animplant with a double-wedged expansion member.

FIG. 18A is a cross-sectional view of an embodiment of an expandable,articulating implant with a wedged insert.

FIG. 18B is a top view of an embodiment of a spacer.

FIG. 19A is a perspective view of an embodiment of an expandable cagewith an elongated insert.

FIG. 19B is a cross-sectional view of the expandable cage embodimentdepicted in FIG. 19A.

FIG. 19C is a view of the inferior surface of the upper body of the cagedepicted in FIG. 19A.

FIG. 20A is a perspective view of an embodiment of a cage including acam and cam ramps.

FIG. 20B is a view of the inferior surface of the upper body of theembodiment of the cage depicted in FIG. 20A.

FIG. 20C illustrates the use of an advancing element to advance the camonto the cam ramp of the cage embodiment depicted in FIG. 20B.

FIG. 20D is a cross-sectional view of an embodiment of an articulatingcage including a cam and cam ramps.

FIG. 21A depicts a perspective view of an embodiment of an expandable,articulating cage with toothed engaging surfaces.

FIG. 21B depicts a perspective view of the cage depicted in FIG. 21A(without the toothed engaging surface) after expansion.

FIG. 22 depicts a perspective view of an embodiment of an insert withfour cam ramps.

FIG. 23 depicts a perspective view of an embodiment of a portion of acage with cam ramps and stabilizers.

FIG. 24A depicts a perspective view of an embodiment of a spacer coupledto an insert of an implant.

FIG. 24B depicts a perspective view of an embodiment of a spacer with aprotrusion.

FIG. 24C depicts a perspective view of an embodiment of a spacer with aprotrusion and a lip.

FIG. 24D depicts a perspective view of an embodiment of an insert with arecess for accepting a protrusion of a spacer.

FIG. 24E depicts a cross-sectional view of an embodiment of a spacerwith a lip coupled to an insert in an expandable cage.

FIG. 25 depicts a perspective view of an embodiment of insertion of aspacer into an expanded cage.

FIG. 26A depicts a perspective view of an embodiment of insertion of aspacer into an expanded cage.

FIG. 26B depicts a perspective view of an embodiment of the cagedepicted in FIG. 26A after insertion of the spacer.

FIG. 26C depicts a perspective view of an embodiment of the cagedepicted in FIG. 26A after insertion of the spacer.

FIG. 27 depicts a perspective view of an embodiment of an expanded cagewith a large profile spacer.

FIG. 28A is a side view of an embodiment of a facet replacement device,featuring a rod with two washer-type heads.

FIG. 28B is a side view of an embodiment of a portion of a facetreplacement device, featuring a rod with a single washer-type head.

FIG. 28C is a cross-sectional view of an embodiment of a pedicle screwfeaturing a locking screw head.

FIG. 28D is a cross-sectional view of an embodiment of a pedicle screwfeaturing a head-locking insert that allows translation and rotation ofa rod.

FIG. 29A is a side view of an embodiment of a portion of a facetreplacement device, featuring a rod having a ball joint.

FIG. 29B is a side view of an embodiment of a portion of a facetreplacement device featuring a retaining plate.

FIG. 29C is a top view of an embodiment of a portion of a facetreplacement device featuring a retaining plate.

FIG. 29D is a top view of an embodiment of a portion of a facetreplacement device featuring a combination multi-axial pedicle screw andretaining bar with post-type pedicle screw system.

FIG. 29E is a side view of an embodiment of a post-type pedicle screw.

FIG. 29F illustrates attachment of the retaining bar to the post-typepedicle screw.

FIG. 30 is a posterior view of a portion of a human spine afterreconstruction and implantation of an embodiment of an artificialfunctional spinal unit including an expandable implant and a facetreplacement device.

FIG. 31A is a perspective view of an embodiment of a portion of a facetreplacement device.

FIG. 31B is a cross-sectional view of the facet replacement devicedepicted in FIG. 31A.

FIG. 31C is a cross-sectional view of the facet replacement devicedepicted in FIG. 31A.

FIG. 31D is a perspective view of an embodiment of a reduced diameterportion of a rod resting in a pedicle screw head of a facet replacementdevice.

FIG. 32 is a perspective view of an embodiment of a portion of a facetreplacement device with a retainer to limit the motion of a rod.

FIG. 33A is a perspective view of an embodiment of a portion of a facetreplacement device designed to couple to a plate with a T-shaped crosssection.

FIG. 33B is a cross-sectional view of the facet replacement devicedepicted in FIG. 33A.

FIG. 34A is a perspective view of an embodiment of a portion of a facetreplacement device including a pedicle screw with a ball joint.

FIG. 34B is a cross-sectional view of the facet replacement devicedepicted in FIG. 34A.

FIG. 34C is a cross-sectional view of the facet replacement devicedepicted in FIG. 34A.

FIG. 35 is a perspective view of an instrument for installing andexpanding an implant.

FIG. 36 is a detail view of a distal end of an instrument for installingand expanding an implant.

FIG. 37 is a detail view of a proximal end of an instrument forinstalling and expanding an implant.

FIG. 38 is a perspective view of an expandable implant held by aninstrument including a holding device and expansion driver.

FIG. 39 is a perspective view of an instrument for installing anexpandable implant including a spacer.

FIG. 40 is a perspective top view of an expandable implant held by aninstrument with a partially inserted spacer.

FIG. 41 is a perspective bottom view of an expandable implant with apartially inserted spacer.

FIG. 42 is a perspective view of a holding device including opposingarms with ball detent mechanisms.

FIG. 43 is a perspective view of a holding device including opposingarms coupled by a coil spring.

FIG. 44 is a perspective view of a holding device including opposingspring arms.

FIG. 45 is a perspective view of a holding device with shape memoryalloy arms.

FIG. 46 is a perspective view of an implant held in a holding deviceincluding upper and lower holding arms.

FIGS. 47A-47D illustrate use of an instrument to expand an implant andinstall a spacer.

FIG. 48 is a perspective view of a distal end of an instrument includinga holding device with a slide.

FIG. 49 is a perspective view of an instrument with a holding devicecoupled to a control member.

FIG. 50A is a side view of a dual rod instrument during guidedadvancement of a spacer.

FIG. 50B is a side view of a dual rod instrument with one rod positionedto impact the spacer between upper and lower bodies of an implant.

FIG. 51 is a cross-sectional view of an instrument including a drivingportion that directly engages an insert for expanding an implant.

FIGS. 52A and 52B are side views of an instrument including multiplerods with threaded ends.

FIG. 53 is a schematic end view of a head of a fastener for a spinalsystem.

FIG. 54 is a schematic end view of a driver for a fastener of a spinalsystem.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but to the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION

As used herein, “implant” generally refers to an artificialintervertebral implant or cage. The shape and/or size of an implant orother device disclosed herein may be chosen according to factorsincluding, but not limited to, the surgical approach employed forinsertion (e.g., anterior or posterior), the intended position in thespine (e.g., cervical or lumbar), and a size of the patient. Forexample, cervical implants may range from about 6 mm to about 11 mm inheight, and lumbar implants may range from about 10 mm to about 18 mm inheight. Heights outside these ranges may be used as required by apatient's anatomy. In general, implants with a substantially round crosssection may range from about 14 mm to about 26 mm in diameter, andimplants with a substantially square cross section may range from a sizeof about 14 mm square to a size of about 26 mm square. Implants that aresubstantially rectangular or trapezoidal may range from about 8 mm toabout 12 mm along short side of the implant to about 24 mm to about 30mm along a long side of the implant. As used herein, “c-shaped” implantsgenerally refer to implants with an arcuate shape. Some c-shapedimplants may be slightly curved (e.g., “banana-shaped”), while otherc-shaped implants may have a higher degree of curvature (e.g., moreclosely approximating a “c”).

It is to be understood that implants described herein may includefeatures not necessarily depicted in each figure. In some embodiments,an endplate engaging surface of any implant may have regularly orirregularly spaced protrusions of uniform or various shapes and sizes tofacilitate retention of the implant in a desired position betweenvertebrae. For example, an endplate engaging surface of an implant mayinclude teeth or ridges. In some embodiments, members of an implant mayinclude one or more openings to accommodate packing of bone graftmaterial and/or to allow for bone ingrowth. In certain embodiments, oneor more surfaces of an implant may include material, such asosteoconductive scaffolding, to enhance integration of the implant in apatient's spine. In some embodiments, a substance to be delivered to apatient's body may be included in a portion of the implant for deliveryto the insertion site. In certain embodiments, implants depicted hereinmay include features allowing the implant to provide a desired lordoticangle (e.g., up to about 15° between vertebrae.

As used herein, an “expandable” implant generally refers to an implantdesigned such that a height of the implant and/or a separation distancebetween two parts of the implant may be increased. In some embodiments,an implant may be expanded after insertion of the implant in a humanspine. In certain embodiments, a height of an implant may be decreasedafter the implant has been expanded during insertion in a human spine.In other embodiments, expansion of an implant may be substantiallyirreversible after insertion in a human spine.

As used herein, an “articulating” implant generally refers to an implantdesigned such that at least two members of the implant are capable ofundergoing rotational motion with respect to each other in at least onedirection after insertion in a human spine. In some embodiments, one ormore members of an articulating implant may be capable of rotating inmore than one direction with respect one or more other members of theimplant after insertion in a human spine to allow, for example,anterior-posterior rotation and/or lateral bending. In some embodiments,rotation may occur about fixed axes. In certain embodiments, an axis ofrotation may change as one member of an implant rotates relative toanother member of the implant. In some embodiments, one or more membersof an articulating implant may be capable of translating with respect toone or more other members of the implant. As used herein, anarticulating implant may also be described as “functional” or “dynamic”.

Implant embodiments depicted herein may be expandable and/orarticulating. In certain embodiments, expansion of an implant afterinsertion in a human spine may allow articulation of the implant. Thatis, the implant may not display articulating motion before expansion ofthe implant in a human spine. In other embodiments, expansion of animplant after insertion in a human spine may allow an increased range ofmotion (increased articulation) between at least two members of theimplant. As used herein, “insertion” of an implant in a human spine mayrefer to assembly, insertion, positioning, and/or expansion of theimplant.

As used herein “facet replacement device” generally refers to a facetreplacement device. For simplicity, a portion of a facet replacementdevice may generally be referred to as a facet replacement device. Thefacet replacement devices disclosed herein generally allow forrotational and/or translational motion of one or more portions of thefacet replacement device including, but not limited to, a plate orelongated member (e.g., rod, bar, rail). Pedicle screws of facetreplacement devices disclosed herein may retain multi-axial characterafter insertion of the facet replacement device. As used herein,“pedicle screw” refers to a portion of a facet replacement device thatcouples to bone. As used herein, “pedicle screw head” refers to aportion of a facet replacement device that accepts an elongated member.As used herein, “pedicle screw” and “pedicle screw head” may be separatecomponents that may be assembled for use in a facet replacement device.

As used herein, “coupled” includes a direct or indirect coupling unlessexpressly stated otherwise. For example, a control member may bedirectly coupled to a driver or indirectly coupled by way of anintermediate shaft. As used herein, “member” includes an individualmember or a combination of two or more individual members. A “member”may be straight, curved, flexible, rigid, or a combination thereof. Amember may have any of various regular and irregular forms including,but not limited to, a rod, a plate, a disk, a cylinder, a disk, or abar.

An implant may be constructed of one or more biocompatible metals havinga non-porous quality (e.g., titanium) and a smooth finish. In someembodiments, an implant may be constructed of ceramic and/or one or moreother suitable biocompatible materials, such as biocompatible polymers.Biocompatible polymers include, but are not limited to,polyetheretherketone resin (“PEEK”). In certain embodiments, an implantmay be constructed of a combination of one or more biocompatible metalsand one or more ceramic and/or polymeric materials. For example, animplant may be constructed of a combination of biocompatible materialsincluding titanium and PEEK.

FIG. 1 depicts a top view of an embodiment of an expandable,articulating implant. Implant 100 may be substantially cylindrical.FIGS. 2A and 2B depict a side cross-sectional view of implant 100. Insome embodiments, implant 100 may include upper body 102 and lower body104. As used herein, “body” may be of unitary construction or mayinclude two or more members. References to “upper body” and “lower body”are chosen for convenience of description of the figures. In someembodiments, an implant may be inserted in a human spine with the “upperbody” superior to the “lower body”. In some embodiments, an implant maybe inserted in a human spine with the “lower body” superior to the“upper body”. In certain embodiments, upper and lower bodies of animplant may be substantially interchangeable. Similarly, “inferior” and“superior” surfaces are also named for convenience of description andmay assume “superior” and “inferior” positions, respectively, uponinsertion.

Implant 100 may include upper body 102 and lower body 104 in asubstantially planar configuration. In some embodiments, superiorsurface 106 of upper body 102 and inferior surface 108 of lower body 104may include (e.g., be coupled to) osteoconductive scaffolding 110 (e.g.,an osteoconductive mesh structure). Vertebral bone from a patient'sspine may grow through osteoconductive scaffolding 110 after insertionof implant 100. In some embodiments, osteoconductive scaffolding 110 mayinclude spines and/or barbs that project into and secure against thebony endplates of the adjacent vertebral bodies upon expansion of theimplant, reducing the possibility of subluxation and/or dislocation.

In some embodiments, a shape of recess 116 and insert 118 may besubstantially the same as a shape of upper body 102 and/or lower body104. In certain embodiments, a shape of insert 118 may be different froma shape of upper body 102 and/or lower body 104. For example, a shape ofinsert 118 may be oval or round, and upper body 102 and/or lower body104 may be c-shaped. Implant 100 may include expansion member 124.Expansion member 124 may be inserted into opening 126 to elevate insert118 from recess 116.

In some embodiments, at least a portion of inferior surface 112 of upperbody 102 may be concave. In certain embodiments, superior surface 114 oflower body 104 may include recess 116. Recess 116 may include, but isnot limited to, a channel or groove. In some embodiments, recess 116 mayhave a rectangular cross section that extends along lower body 104 inthe medial-lateral direction. In certain embodiments, a shape of recess116 may be substantially the same as a shape of upper body 102 and/orlower body 104. Insert 118 may be positioned in recess 116 on superiorsurface 114 of lower body 104. In some embodiments, inferior surface 120of insert 118 may be substantially flat. In some embodiments, at least aportion of superior surface 122 of insert 118 may be convex. A convexportion of superior surface 122 of insert 118 may articulate with aconcave portion of inferior surface 112 of upper body 102, allowingrotation of upper body 102 with respect to lower body 104.

In some embodiments, one or more expansion members may be used toincrease a height of an implant and/or increase a separation distancebetween two or more members of an implant by engaging a portion (e.g.,an insert) of the implant. In some embodiments, an expansion member maybe a part of the implant. That is, the expansion member may remaincoupled to the implant after insertion of the implant in a human spine.For example, expansion members may include, but are not limited to,screws, plates, wedges, and/or a combination of two or more of theseelements. In some embodiments, an expansion member may be a tool,instrument, or driver that is used to expand the implant duringinsertion but does not remain as part of the implant followinginsertion. In certain embodiments, an expansion member may be used toelevate an insert with respect to the lower body of the implant, therebyincreasing a height of the implant and/or increasing a separationdistance between two or more members of the implant. In certainembodiments, an expansion member may be used to translate and/or rotatean insert with respect to a body of the implant (e.g., upper body, lowerbody), thereby increasing a height of the implant and/or increasing aseparation distance between two or more members of the implant.

As depicted in FIGS. 2A and 2B, expansion member 124 may be a screw.Expansion member 124 may be inserted through opening 126 and belowinsert 118 to elevate the insert from lower body 104. In someembodiments, opening 126 may be threaded to accept a threaded expansionmember. In certain embodiments, opening 126 may include features (e.g.,notches) to allow stepwise insertion of an expansion member. Forexample, an expansion member may enter opening 126 in a ratchetingmotion. In some embodiments, a void space may be created between insert118 and the bottom of recess 116 adjacent to the expansion member.

FIGS. 3A and 3B depict side cross-sectional views of implant 100 afterinsertion of expansion member 124 (e.g., after expansion of the implant)such that concave inferior surface 112 of upper body 102 is able toarticulate with convex superior surface 122 of insert 118. FIG. 3Adepicts implant 100 with upper body 102 rotated with respect to lowerbody 104 to undergo extension. FIG. 3B depicts implant 100 with upperbody 102 rotated with respect to lower body 104 to undergo flexion. Insome embodiments, stabilizers 128 may be used to maintain alignment ofupper body 102 and lower body 104 during insertion, expansion, and/orarticulation of implant 100. Stabilizers 128 may include, but are notlimited to, cables, retaining pegs, elastomeric bands, springs, and/orcombinations thereof.

FIGS. 4A and 4B illustrate the expansion of implant 100 in more detail.As shown in FIG. 4A, prior to expansion of implant 100, upper body 102may rest upon lower body 104. Inferior surface 120 of insert 118 mayrest upon the bottom of recess 116, which extends along a portion oflower body 104. In some embodiments, a surface of insert 118 may haveangled portion 130. In some embodiments, an angled portion may be awedge-shaped portion. In certain embodiments, an angled portion mayinclude a curved surface or other surface to facilitate elevation ofinsert 118 from lower body 104. Angled portion 130 may facilitate thelifting of insert 118, allowing expansion member 124 to engage inferiorsurface 120 of insert 118. Following insertion of expansion member 124(e.g., following expansion to a desired intervertebral disc height 132),inferior surface 120 of insert 118 may rest upon the expansion memberwith upper body 102 raised above lower body 104, as depicted in FIG. 4B.

After expansion of implant 100, the implant may be secured in place in ahuman spine with one or more fasteners (e.g., one or more buttressscrews). FIG. 4C illustrates an embodiment utilizing fastener 134. Lowerbody 104 may include portion 136 with one or more openings 138 definedtherethrough. One or more fasteners 134 may be inserted through portion136 and secured into a vertebral body. In some embodiments, fastener 134may be a screw (e.g., a buttress screw).

In some embodiments, an implant may be secured in place with a portionof an expansion member. As shown in FIG. 4D, expansion member 140 mayinclude portion 142 with one or more openings 138 defined therethrough.In some embodiments, portion 142 may be a keel. After expansion member140 is impacted into place, one or more screws 134 may be insertedthrough portion 142 and secured into a vertebral body. Expansion member140 and lower body 104 may also include complementary engaging portion144 to secure expansion member 140 with lower body 104.

FIG. 4E illustrates implant 100 secured between vertebrae of a humanspine. One end of portion 142 may be secured onto lower body 104 ofimplant 100. Portion 142 may be rotated after placement of the device inthe intervertebral space. After rotation of portion 142, the portion issecured to the vertebral body above or below implant 100 with one ormore fasteners 134 (e.g., screws). FIG. 5 depicts implant 100 followinginsertion in a spinal column. In some embodiments, implant 100 may beposteriorly inserted and expanded through void space 146 created byremoval of a facet joint.

FIG. 6A depicts a top view of an embodiment of a c-shaped expandableimplant. Implant 148 may include insert 118. In some embodiments, insert118 may be substantially the same as a shape of an upper body and/orlower body of implant 148. In certain embodiments, a shape of insert 118may be different from a shape of upper body 102 and/or lower body 104.For example, a shape of insert 118 may be oval or round, and upper body102 and/or lower body 104 may be c-shaped. Implant 148 may include twoor more expansion members 124. Expansion members 124 may be insertedinto openings 126 to elevate insert 118 from recess 116.

FIGS. 6B and 6C illustrate the insertion of expansion members intoc-shaped implants. In the embodiment depicted in FIG. 6B, expansionmembers 124 for implant 148 may be screws. One or more expansion members124 may be inserted through one or more openings 126. In someembodiments, one or more openings 126 may be threaded. In certainembodiments, as shown in FIG. 6C, implant 150 may include expansionmember 152. Expansion member 152 may be an elongated or curved membersized and/or shaped for insertion through opening 126. In someembodiments, expansion member 152 may have an angled or wedge portion.Opening 126 may be non-threaded. Expansion member 152 may be impacted ordriven through opening 126 into recess 116 to engage insert 118. Recess116 may be an arcuate channel or a groove shaped and/or sized tofacilitate insertion of expansion member 152 before or after implant 150has been positioned between vertebrae of a human spine. A shape ofexpansion member 152 may be complementary to a shape of recess 116.Engaging insert 118 with expansion member 152 may elevate the insertfrom the lower body of implant 150, increasing a separation distancebetween the upper body and the lower body of the implant. In someembodiments, member 154 may be used to retain expansion member 152 inrecess 116. Member 154 may be, for example, a cap or set screw that fitsthrough opening 126 into a portion (e.g., a threaded portion) of recess116.

FIG. 6D depicts an alternative embodiment for posteriorly securing anexpansion member in a c-shaped implant. Expansion member 156 may be anexpansion plate. Expansion member 156 may be inserted through opening126 of implant 158. Expansion member 156 may be inserted posteriorlythrough opening 126 to slidingly engage insert 118 in implant 158 in themedial-lateral direction. After expansion, member 160 may be inserted inrecess 116. In some embodiments, member 160 may be a retainer plate. Insome embodiments, member 160 may substantially fill recess 116. Incertain embodiments, member 160 may include a securing device such as,for example, a screw.

FIGS. 7A and 7B depict a cross-sectional view of another embodiment ofan expandable, articulating implant. Implant 162 may include upper body102, lower body 104, insert 164, expansion member 152, and set screw 166or similar device. Insert 164 may include one or more stops 168. In someembodiments, stop 168 may be a lip or ledge around a circumference ofinsert 164. In certain embodiments, insert 164 may include angledportion 130. In certain embodiments, expansion member 152 may includeangled portion 170. Before insertion of expansion member 152 into recess116, inferior surface 112 of upper body 102 may rest on superior surface114 of lower body 104.

With insert 164 positioned in recess 116 of lower body 104, expansionmember 152 may be inserted into recess 116. Angled portion 170 ofexpansion member 152 may engage angled portion 130 of insert 164 andexpand implant 162. In some embodiments, set screw 166 may be used toinhibit backout of expansion member 152 after insertion of the expansionmember. In certain embodiments, set screw 166 may be used to advanceexpansion member 152 as well as to inhibit backout of the expansionmember.

After expansion of implant 162, a separation distance between inferiorsurface 112 of upper body 102 and superior surface 114 of lower body 104may allow articulation of the upper body with convex superior surface122 of insert 164. FIG. 7A depicts implant 162 after expansion. Asdepicted in FIG. 7A, upper body 102 is substantially parallel to lowerbody 104. FIG. 7B depicts implant 162 following articulation of upperbody 102 with respect to lower body 104. As depicted in FIG. 7B, stops168 may limit an angular range of motion of upper body 102 with respectto lower body 104. In some embodiments, a shape and/or thickness ofstops 168 may limit a range of rotation of upper body 102 with respectto lower body 104 to less than about 20°. For example, a range ofrotation of upper body 102 may be limited to less than about 5°, lessthan about 10°, or less than about 15°. A range of rotation may dependupon, for example, a shape (e.g., round, ellipsoidal, etc.) of theconvex portion of superior surface 122 of insert 164.

FIGS. 8A and 8B depict different cross-sectional views of an embodimentof an expandable, articulating c-shaped implant. As shown in FIG. 8A,implant 172 depicts recess 116 designed to accept arcuate expansionmember 152. Implant 172 may have opening 126 on an end (e.g., a shortside) of the implant. Expansion member 152 may be impacted into placethrough opening 126 to elevate insert 118 from lower body 104 afterimplant 172 has been positioned in an intervertebral space. Recess 116,as well as expansion member 152, may have substantially the same shape(e.g., substantially the same curvature) as a portion of the upper bodyand/or the lower body of implant 172. In some embodiments, a portion ofinsert 118 may be oval or round (e.g., ellipsoidal, spherical) to allowimproved biomechanical motion of the implant. In some embodiments, abottom of recess 116 may include a feature (e.g., an integral part ofthe lower body or an element coupled to a portion of the lower body)designed to retain expansion member 152 in position after expansion. Forexample, as depicted in FIG. 8B, surface 174 of recess 116 may includelip 176 or other feature designed to retain expansion member 152 in therecess. During insertion of implant 172, a surgeon may force expansionmember 152 over lip 176 into place. Passage of expansion member 152 overlip 176 and into place may allow the surgeon to feel when expansionmember 152 has been properly inserted. In some embodiments, lip 176 mayinhibit dislocation of the implant (e.g., backout of expansion member152).

FIGS. 8C and 8D depict cross-sectional views of an embodiment of anexpandable, articulating implant. Implant 178 may include stabilizers180. Stabilizers 180 may be coupled to lower body 104 and may extendfrom the lower body into openings 182 in upper body 102. Stabilizers 180and/or openings 182 may be of various sizes and/or shapes. For example,Stabilizers 180 may be substantially round and openings 182 may besubstantially oval, allowing torsional mobility of upper body 102. Insome embodiments, stabilizers 180 may be captive. Stabilizers 180 mayinhibit dislocation of upper body 102 from lower body 104 duringflexion, extension, and/or torsional motion of implant 178. As shown inFIG. 8D, when implant 178 is flexed or extended, stabilizers 180 mayinhibit dislocation of upper body 102 from lower body 104.

The disclosed techniques of expanding an implant by insertion of anexpansion member may also be employed to expand a PLIF or TLIF cage.FIGS. 9A-9C depict views of an embodiment of an expandable cage. FIG. 9Adepicts a top view of cage 184. FIG. 9B depicts a cross-sectional viewof cage 184 before expansion. In some embodiments, cage 184 may includecage element 186 and insert 188. Insert 188 may be positioned in cageelement 186. In certain embodiments, cage element 186 may includeosteoconductive scaffolding 110. For example, cage element 186 mayinclude osteoconductive scaffolding 110 on inferior surface 190. Anosteoconductive substance may be placed in osteoconductive scaffolding110 to promote bone growth into cage 184. In some embodiments, cageelement 186 may include opening 192 through superior surface 194.

In some embodiments, insert 188 may include member 196 having inferiorsurface 198 and superior surface 200. In some embodiments, member 196may be substantially planar (e.g., a plate). In certain embodiments,osteoconductive scaffolding 202 may be coupled to superior surface 200of member 196. Member 196 may include angled portion 130. Angled portion130 may facilitate expansion of cage 184 (e.g., elevation of insert 188)upon insertion of expansion member 204. Expansion member 204 may beinserted into opening 206 of cage element 186 and advanced (e.g.,impacted, driven) to engage angled portion 130 of member 196. FIG. 9Cdepicts a cross-sectional view of expanded cage 184. In someembodiments, lip 176 may inhibit dislocation of expansion member 204after expansion of cage 184. In certain embodiments, lip 176 and/or oneor more other features may secure expansion member 204 in cage element186 in such a way that a surgeon may sense tactilely when the expansionmember is fully inserted in cage 184.

FIGS. 9D and 9E depict cross-sectional views of an embodiment of anexpandable cage. FIG. 9D depicts cage 208 before expansion. Insert 210of cage 208 may include osteoconductive scaffolding 212 coupled tosuperior surface 214 of member 216. In some embodiments, osteoconductivescaffolding 212 may have a T-shaped cross-section, such that theosteoconductive scaffolding rests upon superior surface 218 of cageelement 220, providing an increased surface area between theosteoconductive scaffolding and the bony endplates within theintervertebral space.

In some embodiments, expandable cages may be expanded in two or moredimensions. FIG. 9F depicts an embodiment of a cage that may be expandedin two dimensions. Cage 222 may include cage element 186 and inserts188. Cage element 186 may include opening 224 through inferior surface190 as well as opening 192 through superior surface 194. Two inserts 188may be positioned in cage element 186. As expansion member 204 isinserted into cage element 186 between inserts 188, the inserts may beforced through openings 192, 224 to engage the bony endplates within theintervertebral space.

FIGS. 10A, 10B, 11A, and 11B depict an embodiment of a lordotic,c-shaped expandable, articulating implant. The lumbar spine is lordotic,thus the anterior disc height is naturally larger than the posteriordisc height. Therefore, an expandable implant for the lumbar spine mayadvantageously expand into a lordotic position. FIG. 10A depicts aposterior view of implant 226. FIG. 10B depicts a top view of implant226. FIGS. 11A and 11B depict cross-sectional views of implant 226before and after expansion of the implant, respectively.

Implant 226 may include upper body 228 and lower body 230. Lower body230 may include two or more members. In some embodiments, members oflower body 230 may be coupled (e.g., hinged). Portions of upper body 228and lower body 230 may be substantially parallel before expansion ofimplant 226. In some embodiments, superior surface 106 of upper body 228and inferior surface 108 of lower body 230 may include osteoconductivescaffolding 110. In certain embodiments, at least a portion of inferiorsurface 112 of upper body 228 may be substantially concave.

Lower body 230 may include lower portion 232 and upper portion 234. Insome embodiments, lower portion 232 and upper portion 234 of lower body230 may be coupled with hinge 236. Hinge 236 may effectively fixposterior disc height 238 (shown in FIG. 11B). In certain embodiments,inferior surface 240 of upper portion 234 may be substantially flat. Incertain embodiments, at least a portion of superior surface 242 of upperportion 234 may be convex. Lower portion 232 and inferior surface 240 ofupper portion 234 may be substantially parallel prior to expansion. Insome embodiments, lifting mechanism 244 may be located proximateanterior end 246 of lower portion 232. Following insertion of implant226 in an intervertebral space, lifting mechanism 244 may be engaged toincrease a height of anterior end 246 of implant 226. Increasing aheight of anterior end 246 of implant 226 may provide a desired anteriordisc height 248 and proper lordosis. As depicted in FIGS. 11A and 11B,anterior end 246 of upper portion 234 may include notch 250. Notch 250may engage lifting mechanism 244 to secure a height of anterior end 246of implant 226 following expansion.

In some embodiments, at least a portion of inferior surface 112 of upperbody 228 may be concave. A concave portion of inferior surface 112 ofupper body 228 may articulate with a convex portion of superior surface242 of upper portion 234. When viewed in the medial or lateraldirection, as shown in FIGS. 11A and 11B, upper body 228 may includeextension 252 for coupling to elongated member 254. In some embodiments,elongated member 254 may couple upper body 228 to upper portion 234 oflower body 230, thus reducing a possibility of dislocation. FIG. 11Bdepicts the posterior placement of hinge 236 and anterior placement oflifting mechanism 244, with elongated member 254 positioned throughupper body 228 and upper portion 234 of lower body 230.

A lifting mechanism may also be used to achieve desired lordosis withexpandable PLIF and TLIF cages, as shown in FIGS. 12A and 12B. FIGS. 12Aand 12B depict side cross-sectional views of cage 256 before and afterexpansion, respectively. Cage 256 may include upper body 258 and lowerbody 260. In some embodiments, hinge 262 may posteriorly couple upperbody 258 to lower body 260. In certain embodiments, hinge 262 may fixposterior disc height 238 after expansion of cage 256. Superior surface264 of upper body 258 and inferior surface 266 of lower body 260 mayinclude osteoconductive scaffolding 110. Lifting mechanism 244 may beengaged to expand cage 256. In some embodiments, lifting mechanism 244may engage notch 250 after expansion, reducing the possibility fordislocation after insertion and expansion of cage 256. A height oflifting mechanism 244 may be chosen to achieve a desired anterior discheight 248 (e.g., to achieve proper lordosis).

FIG. 13A depicts a cross-sectional view of an expandable, articulatinglordotic implant. FIG. 13B depicts a cross-sectional view of anembodiment of an expandable lordotic cage. Implant 268 in FIG. 13A andcage 270 in FIG. 13B both include expansion member 272 to achieve properlordosis. In some embodiments, expansion member 272 is generallywedge-shaped. In certain embodiments, posterior end 274 of expansionmember 272 may include angled portion 276. Angled portion 276 mayfacilitate expansion of implant 268 and cage 270. Protrusion 280 may belocated on superior surface 278 of the anterior end of expansion member272. As show in FIG. 13A, expansion member 272 may be inserted betweenupper portion 234 and lower portion 232 of lower body 230. Protrusion280 may engage notch 250 to secure a height of implant 268 and cage 270following expansion. Lip 176 or other feature may be located on ananterior end of superior surface 282 of lower portion 232 to reduce thepotential of dislocation of expansion member 272.

FIG. 14A depicts a perspective view of an embodiment of an expandable,articulating implant. Implant 284 may be of any size and/or shape knownin the art. FIGS. 14B and 14C depict cross-sectional views of implant284 before and after expansion, respectively. Implant 284 may includeupper body 286, lower body 288, and elongated member 290. In someembodiments, lower body 288 may include channel 294. Lower body 288 mayinclude openings 296 on opposing walls for receiving elongated member290. In certain embodiments, elongated member 290 may traverse a portion(e.g., a length) of implant 284.

In some embodiments, elongated member 290 may include cam portion 298.In certain embodiments, cam portion 298 may include a spiral camportion. Cam portion 298 may include an arcuate surface that resideswithin channel 294 of lower body 288. In some embodiments, cam portion298 may be coupled to elongated member 290. In certain embodiments, camportion 298 may form an integral part of elongated member 290. In someembodiments, cam portion 298 may wrap partially around elongated member290 with increasing thickness. In some embodiments, as depicted in FIG.14B, implant 284 may be in an unexpanded position when cam portion 298rests at the bottom of channel 294. When elongated member 290 isrotated, cam portion 298 may spin upward to expand implant 284. FIG. 14Cdepicts a cross-sectional view of expanded implant 284.

Superior surface 300 of upper body 286 may contact the bony surface of ahuman vertebra after insertion of implant 284 in a human spine. In someembodiments, an inferior surface of upper body 286 may articulate withthe arcuate surface of cam portion 298. In certain embodiments, upperbody 286 may move back and forth against the arcuate surface of camportion 298. This movement may allow biomechanical motion in a humanspine in which implant 284 has been inserted and expanded. In someembodiments, elongated member 290 may be held in place in openings 296to fix a height of implant 284 after expansion. For example, aratcheting device or fastener (e.g., a set screw) may be used to fix aposition of elongated member 290. In certain embodiments, superiorsurface 300 of upper body 286 and/or inferior surface 302 of lower body288 may be coupled to osteoconductive scaffolding.

FIGS. 15A-15C depict an embodiment of a c-shaped expandable,articulating implant. FIG. 15A depicts a top view of implant 304 withinsert 306. In some embodiments, a portion of insert 306 may besubstantially round, providing a close approximation to naturalbiomechanical motion. FIGS. 15B and 15C illustrate side cross-sectionalviews of implant 304 before and after expansion, respectively. Expansionmember 308 may be inserted through opening 310. In some embodiments,opening 310 may be threaded. Advancing element 312 may be inserted inopening 310 following insertion of expansion member 308. Advancingelement 312 may be used to advance expansion member 308 into positionbelow insert 306. In some embodiments, advancing element 312 may remainin recess 314 to inhibit dislocation of expansion member 308 afterexpansion of implant 304. Use of advancing element 312 (e.g., a setscrew) to advance expansion member 308 into place may reduce impactionduring positioning of the expansion member. Reducing impaction duringpositioning of expansion member 308 may reduce stress on portions of apatient's body during the insertion procedure. It should be noted thatthe expansion member/advancing element combination may be employed withany of the disclosed implants, including cages.

FIGS. 16A and 16B depict perspective views of an embodiment of ac-shaped expandable, articulating implant before and after expansion,respectively. As shown in FIG. 16A, implant 316 may include insert 306and expansion member 308. Insertion of expansion member 308 is achievedby movement of advancing element 312 through opening 310 in an end ofimplant 316. Advancing expansion member 308 with advancing element 312or other device (e.g., a threaded driver) rather than impacting theexpansion member may allow a smaller expansion member to be used. Usinga smaller expansion member may require a shorter access to the implant,allowing an implant to be positioned in a final TLIF position and thenexpanded. For example, a smaller expansion member may require a shorteraccess to the implant. Raising insert 306 with expansion member 308 mayincrease a height of implant 316. Increasing a height of implant 316 mayincrease a range of articulation of the implant after insertion of theimplant in a human spine.

FIG. 17 depicts a perspective view of an embodiment of a portion of anexpandable implant. Implant 318 may include expansion member 320.Expansion member 320 may be advanced with advancing element 322. Asdepicted in FIG. 17, advancing element 322 may be a screw. In someembodiments, advancing element 322 may engage expansion member 320 froma side (e.g., anterior side, posterior side) of implant 318. In someembodiments, expansion member 320 may include two angled portions.Angled portion 324 may engage a portion of implant 318 (e.g., an insertor a portion of an upper body or a lower body). Advancing element 322may engage angled portion 326, thus allowing a component of the forcefrom the advancing element to increase a height of implant 318.Accessing expansion member 320 from a longer side (e.g., posterior side)of implant 318 (PLIF approach) may advantageously require a smallerincision and/or cause less tissue damage during insertion of the implantthan accessing the expansion member from shorter end of the implant(TLIF approach).

FIG. 18A depicts an embodiment of a c-shaped expandable, articulatingimplant designed to accept a spacer between an upper body and a lowerbody of the implant after expansion. Upper body 328 of implant 330 mayinclude upper portion 332 and lower portion 334. Upper portion 332 andlower portion 334 may both have substantially the same c-shape. In someembodiments, superior surface 336 of upper portion 332 may contact abony surface of a vertebral body after insertion of implant 330 in ahuman spine. At least a portion of inferior surface 338 of upper portion332 may be concave. At least a portion of superior surface 340 of lowerportion 334 may be convex. In some embodiments, inferior surface 338 ofupper portion 332 may articulate with superior surface 340 of lowerportion 334.

In some embodiments, inferior surface 342 of lower portion 334 mayinclude angled portion 344. As depicted in FIG. 18A, angled portion 344may be a downward projecting ramp. In certain embodiments, angledportion 346 of expansion member 348 may engage angled portion 344 oflower portion 334 during insertion of the expansion member. Afterexpansion of implant 330, spacer 350 may be inserted in gap 352 betweenlower portion 334 of upper body 328 and lower body 354. In someembodiments, spacer 350 may be a shim. In certain embodiments, asuperior surface of lower body 354 may include one or more guides 356.Guides 356 may include, but are not limited to, protrusions, keyways,rails, grooves, ridges, notches, and/or combinations thereof. Guides 356may align spacer 350 during insertion of the spacer. In someembodiments, guides 356 may inhibit dislocation of spacer 350 afterinsertion of the spacer.

FIG. 18B depicts a top view of an embodiment of spacer 350. In someembodiments, spacer 350 may have substantially the same shape and/orprofile as upper body 328 and/or lower body 354 of implant 330. Incertain embodiments, spacer 350 may be sized such that the spacer issubstantially flush with an outside edge of implant 330. In otherembodiments, spacer 350 may protrude from implant 330 (e.g., from a sidesurface of implant 330) to facilitate alignment and placement of thespacer in the implant. In some embodiments, spacer 350 may include oneor more guides 358. Guides 358 may include, but are not limited to,grooves, keyways, rails, ridges, protrusions, notches, and/orcombinations thereof. Guides 358 on spacer 350 may be complementary toguides on a portion (e.g., upper body, lower body) of an implant.

A height of a spacer may be chosen to provide a desired expanded heightof an implant. A height of a spacer may be, for example, 2 mm, 3 mm, 4mm, or greater. Spacer height may be chosen to achieve a desired heightof an implant in a patient's spine. In some embodiments, a spacer with avariable thickness may be used to provide lordosis to an implant. Insome embodiments, a spacer may be constructed of biocompatible metal(e.g., titanium). In certain embodiments, a spacer may be constructed ofthe same material as an implant into which the spacer is to be inserted.In other embodiments, a spacer may include elastomeric material (e.g.,silicone) to absorb shock and/or allow additional bending.

FIG. 19A depicts a perspective view of an embodiment of an expandableimplant with an elongated, rotating insert following expansion. Implant360 may include upper body 362, lower body 364, insert 366, andadvancing element 368. Intended placement of implant 360 in the spinemay determine a shape of upper body 362 and lower body 364 (e.g.,c-shaped, round). Superior surface 370 of lower body 364 may includerecess 372. In some embodiments, recess 372 may be a channel. Insert 366may be positioned in recess 372. Insert 366 may remain in recess 372during insertion and expansion of implant 360. In some embodiments,inferior surface 374 of insert 366 may be substantially flat. Insert 366may have an elongated shape with one or more angled portions 376 onsuperior surface 378 of the insert.

As advancing element 368 is advanced, angled portions 376 may engageextensions 450 of upper body 460. Advancement of advancing element 394and rotation of insert 366 may increase a separation distance betweenupper body 460 and lower body 462.

FIG. 19B depicts a cross-sectional view of implant 360 before expansion.During expansion, angled portions 376 on superior surface 378 of insert366 may engage angled portions 380 extending downward from inferiorsurface 382 of upper body 362. As advancing element 368 is advanced intorecess 372 in lower body 364, insert 366 rotates in recess 372 onsuperior surface 370 of lower body 364. In some embodiments, insert 366remains in recess 372 and is not elevated during insertion and expansionof implant 360 in a human spine. As insert 366 is rotated, angledportions 380 of upper body 362 slide up the angled portions 376 ofinsert 366, and the upper body is elevated above lower body 364 toincrease a height of implant 360 and/or to increase a separationdistance between the upper body and the lower body. The elongated natureof insert 366 may result in a more stable expanded implant than aninsert of a shorter length. As shown in FIG. 19B, angled portions 376and/or angled portions 380 do not include a platform portion. Thus,implant 360 may have a variable expansion height. An expansion height ofimplant 360 may be secured with advancing element 368 or with a spacerof a desired height.

FIG. 19C depicts a view of an inferior side of upper body 362 withinsert 366 positioned on retaining post 384. Insert 366 may rotatearound retaining post 384. In certain embodiments, retaining post 384may limit a height of implant 360 and/or limit a separation distancebetween upper body 362 and lower body 364.

FIG. 20A depicts a perspective view of an embodiment of a c-shapedexpandable implant with a cam device. Implant 386 may include upper body388, lower body 390, insert 392, and advancing element 394. In someembodiments, advancing element 394 may be an expansion member. In someembodiments, insert 392 may be a cam. As with all of the disclosedembodiments, the placement of implant 386 in the spine will determine ashape of upper body 388 and lower body 390. In some embodiments, lowerbody 390 may include recess 398 in superior surface 396. In certainembodiments, insert 392 may be positioned in recess 398.

In some embodiments, as shown in FIG. 20B, insert 392 may have agenerally cylindrical central portion 400 with opening 402 definedtherethrough. In certain embodiments, insert 392 may include one or moreprojections 404 extending radially from central portion 400. In someembodiments, projections 404 may be arms. Insert 392 may be positionedin recess 398 in lower body 390 on a projection (not shown) extendingupward from a superior surface of the lower body such that theprojection fits in opening 402 of central portion 400 of the insert. Theprojection may align and/or retain insert 392 in a desired position.

In some embodiments, upper body 388 may include one or more angledportions or cam ramps 406 that extend downward from inferior surface 408of the upper body. In certain embodiments, cam ramps 406 may bepositioned such that projections 404 of insert 392 engage the cam rampsas central portion 400 of the insert is rotated around the projection oflower body 390, increasing a separation distance between upper body 388and lower body 390.

In certain embodiments, insert 392 may be rotated via the insertion ofadvancing element 394 (e.g., a screw), as shown in FIG. 20C. In someembodiments, stabilizers 412 may extend downward from inferior surface408 of upper body 388 or upward from a superior surface of lower body390. In some embodiments, stabilizers 412 may be, for example, retainingpegs. Stabilizers 412 may be of various shapes or sizes as required tolimit separation of upper body 388 and lower body 390 as desired. Whenupper body 388 is placed over lower body 390, a large diameter portion(e.g., T-shaped, circular, ellipsoidal, rectangular) of stabilizers 412may be held in openings 414 in lower body 390. In certain embodiments,stabilizers 412 may be inserted through inferior surface 416 of lowerbody 390 and then coupled (e.g., spot welded) to inferior surface 408(e.g., openings in the inferior surface) of upper body 388.

As depicted in FIG. 20A, expansion of implant 386 may increase aseparation distance between upper body 388 and lower body 390 to formgap 418 between the upper body and the lower body. The force ofadvancing element 394 on projections 404 of insert 392 may inhibit theinsert from rotating after expansion, thus inhibiting implant 386 fromundesirably returning to an unexpanded position. In some embodiments, aspacer may be placed in gap 418 between upper body 388 and lower body390 to remove the force on advancing element 394 and to ensure thatimplant 386 remains in an expanded position.

The cam device employed in the embodiment illustrated in FIGS. 20A-C, aswith all the disclosed embodiments of expandable implants, may also beemployed in an articulating, or functional, implant. FIG. 20D depicts across-sectional view of an embodiment of an expandable, articulatingimplant with a cam insert. Insert 392 of implant 422 may be positionedin recess 398 of lower body 390. Projection 424 (e.g., a post) mayextend upward from the superior surface of lower body 390. Insert 392may rotate about projection 424.

Superior surface 426 of upper portion 432 of upper body 388 may contactthe bony surface of an adjacent vertebral body after insertion. At leasta portion of inferior surface 428 of upper portion 432 may be concave.At least a portion of superior surface 430 of lower portion 434 may beconvex. A convex portion of lower portion 434 may be, for example,circular or ellipsoidal in shape. In some embodiments, a circular convexportion may allow biomechanical motion that mimics motion of the humanspine. In certain embodiments, an ellipsoidal convex portion may allowtranslation as well as rotation between, for example, an upper portionand a lower portion of an upper body of an implant. In some embodiments,upper portion 432 and lower portion 434 of upper body 388 may articulatewith respect to each other (e.g., may form a functional joint). Incertain embodiments, cam ramps 406 may extend downward from inferiorsurface 436 of lower portion 434 into lower body 390. Advancing element394 may push against projections 404 of insert 392, thereby rotating theinsert and causing the projections to engage cam ramps 406. Asprojections 404 of insert 392 engage cam ramps 406 and the projectionstravel up the cam ramps, lower portion 434 and upper portion 432 ofupper body 388 may be elevated with respect to lower body 390. As withthe other disclosed embodiments, stabilizers (e.g., captive pegs) mayalso be employed to inhibit separation of upper body 388 from lower body390.

After expansion of implant 422, gap 418 may exist between lower portion434 of upper body 388 and lower body 390. A spacer (e.g., a shim) may beplaced in gap 418 to inhibit implant 422 from returning to an unexpandedposition. A spacer may be of various desirable shapes and/or sizes. Forexample, one side of a spacer may be thicker than another side of thespacer to achieve a desired lordotic angle of the implant. In someembodiments, implant 422 may be inserted in a spine upside down (e.g.,upper body 388 oriented inferior to lower body 390) such that an axis ofrotation of the implant is located closer to the inferior body afterinsertion.

FIGS. 21A and 21B depict a perspective view of embodiments of c-shapedexpandable, articulating implant 422 depicted in FIG. 20D. FIGS. 21A and21B depict retention of stabilizers 412 in lower body 390. As shown inFIG. 21A, superior surface 426 of upper portion 432 of upper body 388and inferior surface 416 of lower body 390 may include teeth 438. Teeth438 may be of any regular or irregular desired size, shape, and/orspacing to promote retention of implant 422 between vertebrae afterinsertion. In some embodiments, teeth 438 may be randomly spacedprotrusions or barbs. In certain embodiments, upper body 388 and/orlower body 390 may include openings to allow for bone ingrowth into aninterior portion of implant 422.

FIG. 21A depicts implant 422 before expansion. In some embodiments, novisible gap may exist between upper body 388 (or upper portion 432) andlower body 390 of implant 422. Thus, a height of implant 422 beforeexpansion may be a minimal height of the implant (e.g., the implant maynot be able to articulate before expansion). In some embodiments, avisible gap may exist between upper body 388 (or upper portion 432) andlower body 390 of implant 422. Thus, a separation distance between upperbody 388 (or upper portion 432) and lower body 390 of implant 422 mayincrease during expansion. FIG. 21B depicts fully expanded implant 422(teeth are not shown for clarity) after advancement of advancing element394. In some embodiments, advancing element 394 may be a screw (e.g., aset screw). In certain embodiments, advancing element 394 may bepositioned on a side (e.g., posterior side) of implant 422 (e.g., for aTLIF application). In certain embodiments, advancing element 394 may bepositioned on an end of implant 422 (e.g., for a PLIF application).

Implant 422 may be fully expanded when platform 440 of cam ramps 406rests on a superior surface of insert 392 (e.g., on a superior surfaceof projections 404 of the insert). In some embodiments, articulation ofupper portion 432 with lower portion 434 may be determined by a degreeof convex curvature of inferior surface 428 of upper portion 432 andsuperior surface 430 of lower portion 434 and/or a relative height (anddepth) of complementary convex/concave contacting surfaces of the upperportion and the lower portion. In certain embodiments, stabilizers 442may be used to align upper portion 432 with lower portion 434 of upperbody 388 and/or to retain the upper portion on the lower portion and/orto limit articulation between the upper portion and the lower portion.As depicted in FIG. 21B, stabilizers 442 may be coupled to lower portion434 of upper body 388 and reside in openings 444 of upper portion 432.In some embodiments, stabilizers 442 may be coupled to upper portion432.

FIG. 22 depicts an embodiment of a portion of an expandable implant. Inthe embodiment depicted in FIG. 22, insert 446 includes four cam ramps448. In other embodiments, an insert may include fewer (e.g., 2 or 3) ormore (e.g., 5 to 12 or more) cam ramps. In contrast to the embodimentdepicted in FIG. 21, in which the cam ramps are a part of the upper bodyof the implant and are stationary during expansion of the implant, camramps 448 may rotate as advancing element 394 rotates insert 446. Insome embodiments, advancing element 394 may rotate insert 446 until aninferior surface of extensions 450 of upper body 452 rest on a superiorsurface (e.g., a platform) of cam ramps 448, as depicted in FIG. 22.Thus, the portion of the insert depicted in FIG. 22 may be used withouta spacer to achieve a fixed separation distance between an upper bodyand a lower body of an implant. In some embodiments, a spacer may beused to provide extra stability and/or to reduce force exerted on camramps 448 of insert 446. In certain embodiments, a spacer may be used toachieve a separation distance less than the fixed separation distancedetermined by a cumulative height of cam ramps 448 and extensions 450 ofupper body 452.

In some embodiments, one or more cam ramps may be positioned on aninferior surface of an upper body or a superior surface of a lower bodyof an implant. FIG. 23 depicts an embodiment of an upper body of animplant. Upper body 464 may include cam ramps 406. Advancement of aninsert up a curved and/or inclined surface of cam ramps 406 maydetermine an expansion height of an implant (e.g., a separation distancebetween an upper body and a lower body of the implant). Stabilizers 466may allow upper body 464 and a lower body of the implant to remaincoupled during and after expansion of the implant. In some embodiments,stabilizers 466 may limit a height of an implant and/or a separationdistance between an upper body and a lower body of the implant. Opening468 of upper body 464 may allow bone graft material to be packed insidethe implant.

In some embodiments, a spacer and an insert may include complementaryportions that allow a spacer to be coupled to an implant (e.g.,reversibly or irreversibly locked into place between an upper body and alower body of the implant). FIG. 24A depicts a perspective view of anembodiment of spacer 470 coupled to insert 472. FIG. 24B depicts aperspective view of spacer 470. FIG. 24C depicts a perspective view ofanother spacer 474. Spacers 470, 474 may include protrusion 476. In someembodiments, protrusion 476 of spacers 470, 474 may be press fit orloose fit into a recess of a member of an implant (e.g., an insert).Fitting (e.g., snapping) protrusion 476 into a recess may advantageouslyprovide a tactile indication to a surgeon that spacer 470, 474 isproperly placed and secured in an implant.

Spacers may have various features designed to facilitate insertion in animplant, retention in an implant, and/or removal from an implant. Forexample, spacer 470 shown in FIG. 24B may include recess 478. Recess 478may allow spacer 470 to be grasped for insertion in an implant and/orfor removal from an implant. Spacer 474 shown in FIG. 24C may includelip 480. Lip 480 may facilitate (e.g., guide) insertion of spacer 474into a gap in an implant. In some embodiments, lip 480 may promoteretention of spacer 474 in a gap between an upper body and a lower bodyof an implant. In some embodiments, a spacer may include a lip around asuperior and/or inferior surface of the entire spacer. In certainembodiments, a spacer may include a lip around a superior and/orinferior surface of a portion (e.g., one side) of a spacer. In someembodiments, a lip may be an external lip or an internal lip. In certainembodiments, a lip on an inferior surface of an upper body or a superiorsurface of a lower body of an implant may be used together with orinstead of a lip on a spacer.

FIG. 24D depicts a perspective view of an embodiment of an insert.Insert 472 may include recess 482. Recess 482 may be complementary to aprotrusion of a spacer (e.g., protrusion 476 of spacers 470, 474). Asdepicted in FIG. 24A, protrusion 476 of spacer 470 may fit securely inrecess 482 of insert 472, inhibiting backout of the spacer after thespacer has been fully inserted. FIG. 24E depicts a perspectivecross-sectional view of spacer 474 with lip 480 used to maintain aseparation distance between insert 472 and an upper body of an implant.

FIG. 25 depicts a perspective view of an embodiment of an expandedc-shaped implant during insertion of a spacer. Implant 484 may includeupper body 486 and lower body 488. Spacer 490 may be inserted in gap 492between upper body 486 and lower body 488. Opening 494 in upper body 486may allow bone graft material to be packed inside implant 484.

FIG. 26A depicts a perspective view of an embodiment of an expandedc-shaped articulating implant during insertion of a spacer. Implant 496may include upper body 498 and lower body 500. Upper body 498 mayinclude upper portion 502 and lower portion 504. Spacer 506 may beinserted in gap 508 between lower body 500 and lower portion 504 ofupper body 498. In some embodiments, stabilizers 510 may extend fromlower portion 504 through openings 512 in upper portion 502 of upperbody 498. A size and/or shape of stabilizers 510 and/or openings 512 mayallow a desired amount of articulation between upper portion 502 andlower portion 504 of upper body 498 (e.g., about a convex portion of thesuperior surface of lower portion).

FIGS. 26B and 26C depict perspective views of implant 496 after spacer506 has been fully inserted. FIG. 26B depicts implant 496 with upperportion 502 angled relative to lower portion 504 of upper body 498.Superior surface of lower portion 504 may include a convex portion(e.g., substantially ellipsoidal or round) that articulates with aconcave portion of inferior surface of upper portion 502 to allowtranslation, rotation, anterior/posterior bending, and/or lateralbending of upper portion 502 relative to lower portion 504 of upper body498, subject to size, shape, and orientation of stabilizers 510 andopenings 512. FIG. 26C depicts implant 496, with details of stabilizers510 and openings 512 visible. Stabilizers 510 may be shaped and orientedsuch that upper portion 502 is angled onto lower portion 504 duringassembly of implant 496. Angled portions of stabilizers 510 and openings512 may allow desired ranges of translational and/or rotational motionof upper portion 502 relative to lower portion 504 while inhibitingseparation of the upper portion from the lower portion.

FIG. 27 depicts a perspective view of an embodiment of a c-shapedexpandable implant with a spacer. Implant 514 may include spacer 516between upper body 518 and lower body 520. Spacer 516 may have a largerprofile than upper body 518 and lower body 520 of implant 514. Thus, aportion of spacer 516 may protrude from a circumference of implant 514.A spacer with a larger profile than an upper body and/or lower body ofan implant may provide torsional support and/or facilitate insertion ofthe spacer during a surgical procedure.

FIG. 28A depicts a side view of an embodiment of a facet replacementdevice. Facet replacement device 522 may include upper pedicle screw 524and lower pedicle screw 526. Rod 528 may be retained in head 530 ofupper pedicle screw 524 and head 532 of lower pedicle screw 526. Rod 528may have washer-type ends 534 that allow for posterior compression, butnot extension.

FIG. 28B depicts a side view of an embodiment of a facet replacementdevice. Facet replacement device 536 may include rod 538. Rod 538 mayinclude a single washer-type end 540 on lower end 542. Head 544 of upperpedicle screw 546 may have threaded locking screw 548, as shown in thecross section in FIG. 28C. Threaded locking screw 548 may hold rod 538in place and inhibit head 544 of pedicle screw 546 from swiveling whileallowing rod 538 to rotate and translate through the head of the pediclescrew.

FIG. 28D depicts a cross-sectional view of an embodiment of ahead-locking insert that may be used in conjunction with a pedicle screwhaving a locking-type head. In some embodiments, insert 550 may have asimilar shape to head 544 of pedicle screw 546. Insert 550 may be ofsolid construction, with opening 554 defined therethrough. In someembodiments, opening 554 may substantially align with the openingdefined through head 544 of pedicle screw 546. As set screw 556 isengaged into head 544 of pedicle screw 546, force is applied to the topof insert 550 and is transferred to the bottom of the head. The forcelocks head 544 of pedicle screw 546, as with conventional lockingpedicle screws; however, the force is not transferred to rod 538. Withno force transferred to rod 538, the rod may rotate in and translatethrough head 544 of the pedicle screw. Alternatively, a shorter insert550 (e.g., threaded only part way into head 544) may be used to inhibita transfer of force to the bottom of the head such that the pediclescrew head undergoes multi-axial motion while retaining the rod in thehead.

FIG. 29A depicts a side view of an embodiment of a facet replacementdevice. Facet replacement device 558 may include upper pedicle screw 560and lower pedicle screw 562. Rod 564 may be retained within heads ofpedicle screws 560, 562. Both pedicle screws 560, 562 may be securedwith locking screws 566 that inhibit heads 568, 570 of the pediclescrews from swiveling while allowing rotation and/or translation of rod564. Rod 564 may include rod members 572, 574 coupled via ball joint576. Ball joint 576 may allow for a generally upward rotation, away fromthe bony surfaces of the vertebrae to which pedicle screws 560, 562 aresecured, but inhibit a generally downward rotation, which would bringthe ball joint in contact with the vertebrae to which the pedicle screwsare secured.

FIGS. 29B and 29C depict side and top views, respectively, of anembodiment of a facet replacement device. Facet replacement device 578may include upper pedicle screw 580 and lower pedicle screw 582 havingpost-type heads 584, 586. Rather than the previously described rod,retaining plate 588 may be included. Elongated openings 590 may bedefined through retaining plate 588 positioned on the post-type heads584, 586 of pedicle screws 580, 582. Post-type heads 584, 586 may beallowed to move in elongated openings 590, providing a limited range ofmotion. Employing cushioning pads 592 made of rubber or otherelastomeric biocompatible material may dampen movement of retainingplate 588. Post-type heads 584, 586 may also include threaded orlockable caps 594 to inhibit dislocation of retaining plate 588 from thepost-type heads.

FIG. 29D illustrates a pedicle screw having post-type head 584 used inconjunction with a pedicle screw having a locking or non-locking typehead 598. Retaining plate 588 may be formed with rod 600 on one end,which may be slidingly positioned through pedicle screw head 598.

As shown in FIGS. 29E and 29F, post-type heads 604 of pedicle screws 606used in conjunction with retaining plate 588 may also exhibitmulti-axial motion. Post-type head 604 may be coupled to pedicle screw606 with ball joint 608. FIG. 29F shows spacer 610 disposed belowretaining plate 588. Spacer 610 may allow for rotation of ball joint608.

FIG. 30 depicts facet replacement device 558 of FIG. 29A in place on thespinal column. Note that implant 612 has been posteriorly placed withinthe intervertebral space through the void created by the surgicalremoval of the natural facet joint. In addition, ball joint 576 mayrotate in the posterior (upward) direction during posterior compressionto inhibit impact upon the bony surfaces of the spine.

FIG. 31A depicts a perspective view of a portion of an embodiment of afacet replacement device. Facet replacement device 614 may includepedicle screw head 616, pedicle screw 618, lower saddle 620, uppersaddle 622, and set screw 624. Rod 626 may be positioned between lowersaddle 620 and upper saddle 622. Set screw 624 may secure lower saddle620, upper saddle 622, and rod 626 in pedicle screw head 616 of facetreplacement device 614. In some embodiments, a diameter of a portion ofrod 626 held between lower saddle 620 and upper saddle 622 maysubstantially the same diameter as other portions of the rod. Forexample, rod 626 may be of substantially constant diameter. In certainembodiments, a portion of rod 626 held between lower saddle 620 andupper saddle 622 may be reduced in diameter relative to other portionsof the rod. FIG. 31B depicts a cross-sectional view of reduced diameterportion 628 of rod 626 positioned in pedicle screw head 616 of facetreplacement device 614.

FIGS. 31B and 31C depict perspective cross-sectional views of facetreplacement device 614. As shown in FIGS. 31B and 31C, rod 626 may havereduced diameter portion 628 positioned between lower saddle 620 andupper saddle 622. Reduced diameter portion 628 of rod 626 may be securedin opening 630 formed by lower saddle 620 and upper saddle 622. Rod 626may be retained in a desired position between lower saddle 620 and uppersaddle 622 by O-rings 632. As depicted in FIG. 31B, O-rings 632 mayreside in grooves 634 in rod 626. A position of grooves 634 in rod 626may be chosen to allow translation of the rod through opening 630 withO-rings 632 positioned in grooves 634. O-rings 632 may be made of anybiocompatible elastomeric material including, but not limited to,silicone. Grooves 634 may have any desirable cross-sectional shapeincluding, but not limited to, rectangular, square, arcuate, orv-shaped.

As depicted in FIGS. 31B and 31C, opening 630 formed by lower saddle 620and upper saddle 622 may have a diameter that exceeds a diameter of theportion of rod 626 (e.g., reduced diameter portion 628 held between theupper saddle and the lower saddle. With a diameter of opening 630 thatexceeds a diameter of rod 626 held in the opening, the rod may be ableto move relative to pedicle screw head 616 of facet replacement device614. In some embodiments, rod 626 may be able to translate and/or rotatewith respect to pedicle screw head 616. In certain embodiments, rod 626may be able to rotate about axes parallel and/or perpendicular to alongitudinal axis of the rod. As depicted in FIG. 31B, rotation of rod626 about an axis perpendicular to a longitudinal axis of the rod mayresult in tilting or angulation of the rod relative to pedicle screwhead 616. In some embodiments, movement of rod 626 in opening 630 may becushioned by O-rings 632.

FIG. 32 depicts a perspective view of a portion of an embodiment of afacet replacement device that may be used in a 2-level spinalstabilization procedure. Facet replacement device 636 may includepedicle screw head 616, pedicle screw 618, lower saddle (not shown),upper saddle 622, and set screw 624. Retainer 638 may hold rod 626 inopening 630 formed by the lower saddle and upper saddle 622. Opening 630may be sized as noted with respect to facet replacement device 614 (FIG.31) to allow rotational and/or translational motion of rod 626 in theopening. O-ring 632 may cushion movement of rod 626 in opening 630. Rod626 used with facet replacement device 636 may have a substantiallyuniform diameter. That is, facet replacement device 636 does not requirea portion of rod 626 to have a reduced diameter. Therefore, pediclescrew head 616 may be placed at any desired position along a length ofrod 626. Adjustable positioning of pedicle screw head 616 along a lengthof a rod of uniform diameter may allow the use of the facet replacementdevice 636 in a two-level or multi-level spinal stabilization procedure.

Retainer 638 may be a c-shaped element with opening 640. A diameter ofrod 626 may exceed a length of opening 640. Thus, after retainer 638 hasbeen snapped onto rod 626, the retainer may remain securely on the rod.Rotational motion of rod 626 in opening 630 may be limited by relativediameters of rod 626 and opening 630. Translational motion of rod 626through opening 630 may be limited by placement of retainers 638 oneither side of pedicle screw head 616.

FIG. 33A depicts a perspective view of an embodiment of a portion of afacet replacement device including a plate rather than a rod. Facetreplacement device 642 may include pedicle screw 618, pedicle screw head644, and fastener 646. In some embodiments, fastener 646 may be, forexample, a screw. Plate 648 may be coupled between pedicle screw head644 and fastener 646. In some embodiments, plate 648 may have a T-shapedcross section. In certain embodiments, a T-shaped cross section mayprovide a lower profile than a rod, advantageously requiring less spaceat a surgical site. Size, thickness, and dimensions of a T-shaped crosssection may vary as needed for strength, stability, and surgical access.For example, stem portion 650 of plate 648 may be of various heights.

FIG. 33B depicts a cross-sectional view of facet replacement device 642including plate 648. Plate 648 may be coupled to pedicle screw head 644between lip 652 of the pedicle screw head and lip 654 of fastener 646.In some embodiments, fastener 646 may have a threaded portion thatengages a threaded portion inside pedicle screw head 644 (threadedportions not shown). In some embodiments, spacer 656 may be positionedbetween pedicle screw head 644 and fastener 646. In certain embodiments,spacer 656 may fit inside opening 658 in plate 648 (e.g., between theplate and fastener 646). A diameter of opening 658 may be sized suchthat plate 648 can rotate and/or translate relative to pedicle screwhead 644. In some embodiments, spacer 656 may be a bushing or an O-ring.Spacer 656 may be made of elastomeric materials such as, but not limitedto, silicone. Spacer 656 may cushion and/or dampen movement of plate 648relative to pedicle screw head 644 and/or fastener 646 to allow smootherbiomechanical motion after insertion in a human spine.

FIG. 34A depicts a perspective view of an embodiment of a portion of afacet replacement device with a pedicle screw that retains mobilityafter a rod is secured. Facet replacement device 660 may include pediclescrew head 662, pedicle screw 664, upper saddle 666, and set screw 624.Ball joint 668 of pedicle screw 664 may rest in base 670 of pediclescrew head 662. A portion of rod 626 may contact ball joint 668 ofpedicle screw 664. In some embodiments, rod 626 may have a reduceddiameter portion that resides in pedicle screw head 662 and contactsball joint 668 of pedicle screw 664. In other embodiments, rod 626 mayhave a substantially constant diameter.

In some embodiments, an outside portion of upper saddle 666 and aninside portion of pedicle screw head 662 may be complementarily threaded(not shown), such that the upper saddle may be threaded into the head.In certain embodiments, pedicle screw head 662 may be threaded such thatupper saddle 666 may be threaded a limited distance into the head (e.g.,upper saddle 666 does not contact base 670). Set screw 624 may inhibitbackout of upper saddle 666 from pedicle screw head 662. A length ofthreading in pedicle screw head 662 may be chosen such that upper saddle666 may be fully secured in the head without tightening rod 626 ontoball joint 668. Thus, with rod 626 fully secured in head 662, the rodand pedicle screw 664 both retain rotational mobility. In someembodiments, O-rings 632 may be positioned on rod 626 on both sides ofupper saddle 666. Translation of rod 626 in pedicle screw head 662 maybe limited by the placement of O-rings 632 on the rod and/or by aretainer.

FIGS. 34B and 34C depict cross-sectional views of facet replacementdevice 660. As shown in FIGS. 34B and 34C, reduced diameter portion 628of rod 626 may be held loosely between upper saddle 666 and ball joint668 of pedicle screw 664. With threading (not shown) inside pediclescrew head 662 extending only partially down toward the base of thepedicle screw head, upper saddle 666 may secure rod 626 in the pediclescrew head without causing the rod to bear down on ball joint 668 ofpedicle screw 664. With rod 626 and ball joint 668 able to move freely,the rod may retain rotational (and/or translational) mobility afterinsertion of facet replacement device 660 in a human spine.

In some embodiments, instruments may be used to install elements of animplant in a spine. Instruments may also be used to position (e.g.,rotate, translate, expand) elements of an implant in vivo. In certainembodiments, a single instrument may be used to perform multiple stepsof a spinal procedure. For example, an instrument may be used toposition an implant in an intervertebral space and to actuate anexpansion member to expand the implant in the intervertebral space.

FIG. 35 depicts instrument 700 for use in installing and expanding animplant. Instrument 700 may have proximal end 702 and distal end 704.Instrument 700 may include outer shaft 706, driver 708, holding device710, and handle 712. As used herein, “shaft” includes elongated membershaving various regular and irregular cross-sections, including, but notlimited to, round, square, rectangular, hexagonal, or irregular. A shaftmay be solid or hollow.

Instrument 700 may include thumbwheel 714. Thumbwheel 714 may be coupledto driver 708. Thumbwheel 714 may act as a control member for driver708. As used herein, “control member” includes any element that isoperable by a user to control position, orientation, or motion ofanother element. Other examples of control members include, but are notlimited to, a knob, a lever, or a button. In some embodiments, a controlmember may be operated using a tool.

In one embodiment, thumbwheel 714 may be fixedly coupled to driver 708such that driver 708 rotates as thumbwheel 714 is rotated. In anotherembodiment, thumbwheel 714 may be threadably coupled to driver 708 suchthat driver 708 translates along its axis when thumbwheel 714 isrotated.

FIG. 36 depicts a detail view of distal end 704 of instrument 700.Holding device 710 may hold an implant during insertion of the implantbetween two vertebrae. As used herein, “holding device” includes anyelement or combination of elements that may be used to hold, support, orgrip another element, such as an implant, spacer, or insert. Examples ofholding devices include, but are not limited to, a clamp, a clip, or athreaded rod. In some embodiments, a holding device may include one ormore opposing holding elements. For example, as shown in FIG. 36,holding device 710 may include holding arms 716. Holding arms 716 may behinged to base 718. Base 718 may be coupled to outer shaft 706. Holdingarms 716 may be coupled to spring clip 720. Spring clip 720 may maintainholding arms 716 in a closed position (as shown in FIG. 36) unless atleast a predetermined amount of separation force is applied toinstrument 700 and an implant.

Lobes 722 on holding arms 716 may engage complementary surfaces (e.g.,notches, grooves) on an implant or spacer. Engagement between lobes andcomplementary surfaces on an implant or spacer may promote engagementbetween an instrument and an implant or a spacer. Holding arms mayinclude other engaging elements, such as tabs, grooves, or pins. Incertain embodiments, the inner surfaces of holding arms on a holdingdevice may be flat. The inner surfaces of holding arms may be texturedor smooth.

In some embodiments, spring clip 720 may be at least partially made of ashape memory alloy. Spring clip 720 may be actuated by allowing thespring clip to reach a predetermined temperature. When spring clip 720is actuated, the spring clip may urge holding arms 716 outwardly from aclosed position. In one embodiment, spring clip 720 may be actuated bybody heat. In another embodiment, spring clip 720 may be actuated byelectrical current carried by insulated conductors in or on theinstrument.

Base 718 of holding device 710 may allow for passage of driver 708.Driver 708 may include inner shaft 724 and driver head 726. Inner shaft724 may be coupled with thumbwheel 714 (shown in FIG. 35). Driver head726 may have any of various forms suitable for actuating (e.g.,rotating, advancing) a portion of an expansion member or insert. In oneembodiment, a driver head may include external threads that can engageinternal threads on a portion of an implant. Other examples of driverhead types include, but are not limited to, slotted, Phillips, square,hexagonal, or hexalobular. In some embodiments, the driver head mayengage a set screw in the implant.

FIG. 37 depicts a detail view of proximal end 702 of instrument 700.Handle 712 may include grip portion 728 and end portion 730. End portion730 may include a surface suitable for receiving impact by anotherinstrument. Slot 732 may be provided between grip portion 728 and endportion 730. Thumbwheel 714 may partially reside in slot 732. In certainembodiments, surfaces of thumbwheel 714 may have knurls, ribs, orsimilar characteristics to facilitate rotation of the thumbwheel.

Handle 712 may protect portions of the instrument from damage duringuse. For example, handle 712 may protect against damage to threads oninner shaft 724 when another instrument is used to strike instrument700. In one embodiment, a transverse cross section of handle 712 at slot732 may be generally rectangular, as shown in FIG. 37. A rectangularcross section at slot 732 may allow a user to access a sufficientportion of thumbwheel 714 to turn the thumbwheel, but still protectthumbwheel 714 and inner shaft 724 (shown in FIG. 35) from damage. Atransverse cross section of handle at slot 732 may be shapes other thanrectangular, such as square, oval, hexagonal, or irregular.

Although the protecting portions of instrument 700 shown in FIG. 37 arean integral part of handle 712, a protector in other embodiments may bea separate component from the handle. In certain embodiments, aprotector may be removable from an instrument so that a user may accessa driver and/or control member.

FIG. 38 depicts implant 484 held by instrument 700 after driver 708 hasbeen operated to expand the implant. When implant 484 is initiallycoupled to holding device 710, lobes 722 of holding arms 716 may engagein holding recesses 733 on either side of lower body 488. Engagement oflobes 722 in holding recesses 733 may help maintain a position of theimplant during insertion and/or expansion of the implant. Engagement oflobes 722 within holding recesses 733 may place implant 484 in a desiredalignment for insertion between the vertebrae and engagement with anexpansion tool. The location of holding recesses 733 may be selectedaccording to the approach to be used (e.g., TLIF, PLIF) and the locationof an expansion member of the implant. For example, for a TLIF implant,holding recesses may, in some embodiments, be located near bothlongitudinal ends of the implant.

In some embodiments, driver head 726 may engage an insert (e.g., insert472 depicted in FIG. 24D) of an implant. In other embodiments, driverhead 726 may engage a set screw (e.g., advancing element 394 depicted inFIG. 21B) of an implant, which may in turn actuate (e.g., translate orrotate) an insert. Actuation of driver 708 may expand implant 484 to theexpanded position shown in FIG. 38. After implant 484 has been expanded,instrument 700 may be pulled away from the surgical site with enoughforce to overcome the closing force of holding device 710, therebyspreading holding arms 716 apart to allow separation of instrument 700from implant 484 and removal of the instrument from the site. In anotherembodiment, a release mechanism can be used to spread holding arms 716apart.

In some embodiments, an inserter for a spacer may be used in combinationwith an implant holder and/or a driver for an expansion member. In someembodiments, an inserter may include a guide that engages a portion ofan implant holder. The guide may be used to position the spacer near adesired location near the implant and/or to insert the spacer in theimplant. Examples of guides include, but are not limited to, a fork, ahook, a ring, a spring clip, a tab, a rail, or a groove. In someembodiments, an inserter may be used to guide a spacer to a locationnear an implant, such as at a gap between an upper body and a lower bodyof the implant. In certain embodiments, an inserter may be advanced on ashaft to fully insert a spacer between upper and lower bodies of animplant.

FIG. 39 depicts instrument 736 including inserter 738 for holding spacer470. Inserter 738 may include inserter shaft 740, inserter handleportion 742, spacer holding device 744, and guide fork 746. Guide fork746 may engage outer shaft 706. Inserter handle portion 742 may includebend 748. Bend 748 may allow a proximal portion of inserter handleportion 742 to be positioned close to handle 712 so inserter handleportion 742 may be manipulated in a relatively small incision.

In the embodiment shown in FIG. 39, inserter 738 may be easily separatedfrom outer shaft 706. Thus, the surgeon could first insert and expandthe implant, then introduce inserter 738 into the incision. In otherembodiments, an inserter may be permanently coupled to the rest of aninstrument.

FIG. 40 depicts a detail view of implant 484 held by instrument 736, asseen from the upper side of the implant. FIG. 41 depicts a detail viewof implant 484 held by instrument 736, as seen from the lower side ofthe implant. In FIGS. 40 and 41, spacer 470 is partially insertedbetween upper body 486 and lower body 488 of implant 484.

In the embodiment shown in FIG. 40, spacer holding device 744 includesholding arms 716 that are fixed with respect to base 718. Each ofholding arms 716 may include ball detent mechanism 750. FIG. 42 depictsa detail view of ball detent mechanisms 750. Detent springs 752 mayprovide a desired amount of clamping force on spacer 470. In otherembodiments, a spacer holding device may include hinged arms that aresimilar to those of holding device 710 shown in FIG. 36.

Referring again to FIG. 36, it is noted that spring clip 720 may serveas a biasing element to maintain a holding force on the implant. As usedherein, a “biasing element” includes any element that biases a member ofa device toward one position. A biasing element may be a separateelement of a holding device or integral to another element of the device(e.g., a holding arm). Biasing elements include, but are not limited,resilient members such as metal springs or elastomeric bands. Additionalembodiments of holding devices with biasing elements are describedbelow.

FIG. 43 depicts holding device 710 including holding arms 716 hinged tobase 718 and connected by coil spring 754. In one embodiment, coilspring 754 is spot welded to the holding arms. FIG. 44 depicts analternate embodiment of holding device 710 that includes spring arms755. In certain embodiments, spring arms 755 may be made of 302, 314, or316 stainless steel.

FIG. 45 depicts a holding device 710 having holding arms 716 made of ashape memory alloy. Holding arms 716 may be actuated by allowing theholding arms to reach a predetermined temperature. When holding arms 716are actuated, the holding arms 716 may move outwardly from a closedposition. Holding arms 716 may be actuated using body heat, insulatedelectrical current, or another heat source.

FIG. 46 depicts an alternate embodiment of a holding device. Holdingdevice 710 may engage a top surface of implant 484. Notches 756 inimplant 484 may allow the outer surfaces of holding arms 716 to be flushwith the outer surfaces of upper body 486 and lower body 488,facilitating insertion of implant 484 between the vertebrae. In anotherembodiment, a holding device may engage top and bottom surfaces of aspacer for an expandable implant.

FIGS. 47A-47D depict a top view of an expandable implant duringexpansion of the implant and insertion of a spacer between upper andlower bodies of the implant. FIG. 47A depicts implant 484 on instrument700 before expansion of implant 484. Driver head 726 of driver 708 maybe advanced into a tapped through hole in lower body 488 of implant 484until the tip of driver head 726 engages insert 472. Advancement ofdriver head 726 may rotate insert 472 to expand implant 484 between thevertebrae (see FIG. 47B). Holding device 710 may exert sufficient forceon implant 484 to maintain the implant in a fixed position duringactuation of driver 708.

Guide fork 746 of inserter 738 (shown in FIG. 39) may be placed on outershaft 706. Inserter 738 may be advanced on outer shaft 706 to movespacer 470 into position between the upper body and the lower body ofimplant 484 (FIG. 47C). Inserter 738 may be advanced until spacer 470 isfully installed between the upper and lower bodies of implant 484 (FIG.47D). Once spacer 470 is fully installed, instrument 700 and inserter738 may be withdrawn from the surgical site, either together or one at atime.

In certain embodiments, an instrument may include a movable element formaintaining a holding device in a closed position. FIG. 48 depicts adistal end of instrument 758 including slide 760. Slide 760 may includeprojections 762. Projections 762 may define notches 764 at a distal endof slide 760. Bottom surfaces 766 of notches 764 may act as stopsagainst axial motion of holding device 710. Spring clip 720 may biasholding arms outwardly from the closed position shown in FIG. 48. Whenprojections 762 are adjacent to holding arms 716 of holding device 710(as shown in FIG. 48, for example), the projections may inhibit outwardrotation of the holding arms, thereby keeping the holding device in aclosed position. When slide 760 is retracted from holding arms 716(e.g., by moving the slide proximally with respect to the holdingdevice), the holding arms may move apart under the force of spring clip720 to allow release of an implant from the instrument.

Other arrangements may be used to maintain a holding device in a closedposition. For example, a slide may include a cylindrical sleeve thatpasses over the outer sides of a holding device. The inner wall of thesleeve may inhibit the holding arms from moving out of a closedposition.

In some embodiments, a holding device for an implant or spacer may becoupled to a control member, such as a thumbwheel or lever. The controlmember may be operated to selectively hold and release the implant orspacer. FIG. 49 depicts a perspective view of inserter 768 includingholding device 710. Holding arms 716 of holding device 710 may becoupled to coil spring 754 in a similar manner as described aboverelative to FIG. 43. Coil spring 754 may bias holding arms 716 into aclosed position on a spacer. Cable 770 may extend between thumbwheel 714and holding arms 716 through hollow shaft 772. Thumbwheel 714 may beoperated to draw cable 770 away from distal end 704 of instrument 768.Cable 770 may act against the force of coil spring 754 to open holdingarms 716, thereby allowing the spacer to be released from the holdingdevice. Inserter 768 may include guide fork 746. Guide fork 746 mayslidably engage a portion of an implant holder (e.g., the outer shaftshown in FIG. 35) to facilitate positioning of the spacer prior torelease of the spacer. In another embodiment, a control member may beconnected to a locking slide to selectively lock and release a holdingdevice.

FIGS. 50A and 50B depict instrument 774 including a pair of rods forinserting implant 776 having spacer 778. Bottom rod 780 and top rod 782of instrument 774 may be commonly supported on base member 784. Bottomrod 780 may include threaded portion 781. Threaded portion 781 mayengage in a tapped hole in lower body 786 of implant 776. In oneembodiment, tab 787 on spacer 778 may engage a channel or groove in toprod 782 to help guide and/or align spacer 778. Top rod 782 may be usedto guide spacer 778 to a gap between upper body 788 and lower body 786,as shown in FIG. 50A. Once spacer 778 is in position for insertionbetween upper body 788 and lower body 786 of implant 776, top rod 782may be repositioned in base member 784 such that a distal end of top rod782 is behind spacer 778, as shown in FIG. 50B. Top rod 782 can be usedto advance spacer 778 between upper body 788 and lower body 786. Incertain embodiments, top rod 782 may be used to impact spacer 778between upper body 788 and lower body 786.

FIG. 51 depicts alternative embodiment of an instrument 790 includingdriver 708 with driver head 726. Driver head 726 may include threadedportion 792. In one embodiment, threaded portion 792 may be threadedinto a tapped through opening in an upper or lower body of an implant.As threaded portion 792 of driver head 726 is advanced through theopening, a distal tip of driver head 726 may actuate (e.g., translate,rotate) an insert. Instrument 790 may include outer shaft 706 andholding device 710. In certain embodiments, holding device 710 ofinstrument 790 may be shaped to match a contour of an implant or aspacer. In one embodiment, holding device 710 may have an arcuate shape.Driver head 726 may be actuated by thumbwheel 714. Instrument 790 mayinclude removable cover 794. Removable cover 794 may protect thumbwheel714 from damage during use.

FIGS. 52A and 52B depict an alternate embodiment of an instrument forplacing and expanding an implant and inserting a spacer. Instrument 796may include base member 798. Base member 798 may carry holder rod 800,driver rod 802, and inserter rod 804. Holder rod 800 may threadablyengage a tapped hole in lower body 786 to support implant 806. Driverrod 802 may threadably engage through hole 808 in lower body 786. Driverrod 802 may be advanced to actuate insert 810 to increase a separationdistance between lower body 786 and upper body 788, thereby expandingimplant 806. Spacer 812 may be threadably coupled to inserter rod 804.Inserter rod 804 may be guided on base member 798 to advance spacer 812between lower body 786 and upper body 788. Holder rod 800, driver rod802, and inserter rod 804 may be rotated to disengage the rods fromimplant 806. The rods may be removable from base member 798. In someembodiments, inserter rod 804 may be loaded into an open channel in basemember 798.

It will be understood that any or all of the threaded tips on rods 800,802, and 804 may be replaced by other holding devices including, but notlimited to, the holding devices shown in FIGS. 36-44. It will be furtherunderstood that in other embodiments, an instrument may omit one or moreof the implant holder, the expansion driver, or the spacer inserter. Forexample, an instrument may include only an implant holder and anexpansion driver, or only an implant holder and a spacer inserter.

In an embodiments, a driver for components of a spinal system mayinclude a feature for locking with an element of a spinal system. FIG.53 depicts a schematic view of a proximal end of head 816 on fastener818 for a spinal system. Head 816 may include side hole 820. A fastenerfor a spinal system may include, but is not limited to, a set screw, apedicle screw, or a threaded top for a polyaxial screw. FIG. 54 depictsa schematic view of a distal end of driver 822. Driver 822 may includesleeve 824 having socket 826. Driver 822 may include lock element 828.Lock element 828 may retractably extend into socket 826. Button 830 onsleeve may be manually operated to retract lock element 828 from socket826. When sleeve 824 of driver 822 is placed on head 816 of fastener818, lock element 828 of driver 822 may engage in side hole 820.

Engagement of lock element 828 in side hole 820 may inhibit axialseparation of driver 822 from head 816 of fastener 818. A lockingelement may reduce a risk of a fastener disengaging from a tool duringuse. In certain embodiments, lock element 828 may be used to capture abreak-off head of a top for a polyaxial screw. In certain embodiments,driver 822 may be coupled with a detachable handle. In some embodiments,driver 822 may be used with a power tool (e.g., a drill).

In an embodiment, an implant (e.g., for an expanse cage, dynamic cage)may be placed in a human spine using a posterior approach to a diseasedlumbar disc. In some embodiments, the surgeon may use the same approachas is typically used in a microdiscectomy, TLIF, or minimally invasiveposterior exposure. Such procedures involve removing some of the laminaand the medial facet joint. More bone, including the spinous process andthe entire facet may be removed if indicated.

The vital structures involved with the posterior approach are the nerveroots. The exiting root is the root that leaves the spinal canal justcephalad (above) the disc, and the traversing root leaves the spinalcanal just caudad (below) the disc. The thecal sac houses the othernerve roots that exit lower. The triangle between the exiting nerve rootand the traversing nerve root (Pambin's or Cambin's triangle) is theextent of the access to the disc. The triangle may be enlarged byretracting the traversing nerve root medially. If retraction is done toovigorously, however, retraction injuries may occur and seriouscomplications such as nerve root sleeve tear may result, causing spinalfluid leakage, nerve root injury, avulsion and even spinal cord injury.

After the lamina has been removed and the traversing root retractedmedially, the posterior annulus may be exposed. While the root isretracted gently, the surgeon may create an annulotomy. Pituitaryforceps may be used to remove disc material. Successively larger forcepsmay be used until an adequate amount of disc is removed. Care should betaken not to penetrate the anterior annulus and enter theretroperitoneal space. After adequate disc material has been removed,the end plates may be prepared using osteotomes to remove posteriorostephytes and cutting curettes to decorticate the end plates. Theobject of end plate preparation is to remove the cartilaginous tissueand score the cortical bone without completely removing the corticalstrength.

Once the end plates have been prepared, a trial may be placed in thedisc space. The trial should be snug without significantly distractingthe end plates. An unexpanded implant of approximately the same size asthe trial may then be inserted into the disc space. Once positionedanterior to the nerve roots, the implant may be expanded. In someembodiments, a spacer may be introduced following expansion of theimplant. The spacer may include a protrusion, groove, or similar elementthat snaps or locks into place to provide a tactile sensation as thespacer reaches a fully inserted position. A tactile sensation mayprovide the surgeon with positive feedback that the spacer is in place.In certain embodiments, the implant may be further rotated within thespace after the spacer is introduced, according to the preference of thesurgeon.

An expandable implant (e.g., an expanse cage or dynamic device) mayallow a larger device to be placed into the disc from a posteriorapproach without over distracting the nerve roots or the ligaments. Insome embodiments, the implant may be expanded without any overdistraction. This advantage may allow the surgeon to tension theannulus, avoid resection of the anterior longitudinal ligament, anddecompress the nerve roots without requiring over distraction and theattendant possibility of injury to the nerves and ligaments. For reasonsoutlined above, many patients are not suitable candidates for ananterior approach. In one embodiment, an implant of less than about 12mm in width is placed posteriorly without over distraction. In anotherembodiment, an implant of less than about 10 mm in width is placedposteriorly without overdistraction.

In an embodiment, an expandable implant may expand throughout its entirewidth. In some embodiments, an expandable implant may be used forposterior disc height restoration without increasing lordosis. In otherembodiments, an expandable implant may be used for posterior disc heightrestoration with increasing lordosis. In certain embodiments, an implantmay be placed using a TLIF approach. Although some of the descriptionherein relates to a PLIF or TLIF approach, it will be understood thatimplants as described herein may be placed using an anterior approach.

In this patent, certain U.S. patents, U.S. patent applications, andother materials (e.g., articles) have been incorporated by reference.The text of such U.S. patents, U.S. patent applications, and othermaterials is, however, only incorporated by reference to the extent thatno conflict exists between such text and the other statements anddrawings set forth herein. In the event of such conflict, then any suchconflicting text in such incorporated by reference U.S. patents, U.S.patent applications, and other materials is specifically notincorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as examples of embodiments. Elements and materials maybe substituted for those illustrated and described herein, parts andprocesses may be reversed, and certain features of the invention may beutilized independently, all as would be apparent to one skilled in theart after having the benefit of this description of the invention.Changes may be made in the elements described herein without departingfrom the spirit and scope of the invention as described in the followingclaims.

What is claimed is:
 1. An intervertebral implant system for a humanspine, comprising: a first body comprising: a first external surfaceconfigured to be disposed adjacent a first vertebra during use, and afirst internal surface opposite the first external surface; a secondbody comprising: a second external surface configured to be disposedadjacent a second vertebra during use, and a second internal surfaceopposite the second external surface; an elongated insertion instrumentreleasably couplable to the first or second body during use; and aspacer linearly advanced between the first internal surface of the firstbody and the second internal surface of the second body during use,wherein the elongated insertion instrument guides at least a portion ofthe linear advancement of the spacer after the first and second bodieshave been disposed substantially between the first and second vertebraefrom a position remote to the first and second bodies during use, andwherein the linear advancement of the spacer results in expansion of theintervertebral implant such that the first external surface and thesecond external surface move away from one another to expand a height ofthe implant.
 2. The system of claim 1, wherein the spacer is disposed ina gap between the first and second internal surfaces of the first andsecond bodies during use.
 3. The system of claim 1, wherein a leadingend of the spacer comprises a wedge shaped nose.
 4. The system of claim3, wherein at least one of the first or second bodies comprise a rampedsurface engaged by the wedge shaped nose as the spacer is linearlyadvanced during use.
 5. The system of claim 1, further comprising another elongated insertion instrument, wherein the elongated insertioninstruments are located on opposite sides of the spacer during use. 6.The system of claim 5, wherein the elongated insertion instruments eachcomprise longitudinal axis running along their length, and wherein thelongitudinal axes of the elongated insertion instruments are arrangedsubstantially parallel to one another during use.
 7. The system of claim6, wherein the spacer is advanced linearly between the elongatedinsertion instruments in a direction substantially parallel tolongitudinal axes of the elongated insertion instruments.
 8. The systemof claim 1, wherein an interface between the elongated insertioninstrument and the spacer comprises a channel and complementaryprotrusion that guides linear advancement of the spacer.
 9. The systemof claim 8, wherein the spacer comprises a protrusion that engages acomplementary channel of the elongated insertion instrument, and whereinthe complementary channel is formed in the surface of the elongatedinstrument and extends along at least a majority of a longitudinallength of the elongated insertion instrument.
 10. The system of claim 1,further comprising an other elongated insertion instrument, wherein theother elongated insertion instrument is moved linearly to advance thespacer linearly during use.
 11. The system of claim 10, wherein theother elongated insertion instrument engages a trailing end of thespacer and is moved linearly to push the spacer linearly during use. 12.The system of claim 1, wherein at least one of the first or second bodycomprises an instrument engagement feature engaged by a complementarybody engagement feature of the elongated insertion instrument to rigidlycouple the elongated insertion instrument to the first or second bodyduring use.
 13. The system of claim 1, wherein the elongated insertioninstrument is releasably coupleable to the first body and the secondbody during use.
 14. A method of implanting an intervertebral implantinto a human spine, comprising: disposing an upper body into anintervertebral space between an upper vertebra and a lower vertebra,wherein the upper body comprises: a superior surface disposed adjacentthe upper vertebra, and an inferior surface opposite the superiorsurface; disposing a lower body into the intervertebral space betweenthe upper vertebra and the lower vertebra, wherein the lower bodycomprises: an inferior surface disposed adjacent the lower vertebra, anda superior surface opposite the inferior surface; releasably coupling adistal end of an elongated insertion instrument to at least one of theupper body and the lower body; positioning a spacer substantiallyadjacent to the upper and lower bodies after the upper and lower bodieshave been disposed into the intervertebral space between the uppervertebra and the lower vertebra; and linearly advancing a spacer betweenthe inferior surface of the upper body and the superior surface of thelower body, wherein the elongated insertion instrument guides at least aportion of linear advancement of the spacer from a substantiallyproximal end of the elongated insertion instrument to a substantiallydistal end of the elongated insertion instrument, and wherein linearadvancement of the spacer results in expansion of the intervertebralimplant such that the superior surface of the upper body and theinferior surface of the lower body move away from one another to expanda height of the implant.
 15. The method of claim 14, further comprisingreleasing the elongated insertion instrument after the spacer isdisposed between the inferior surface of the upper body and the superiorsurface of the lower body.
 16. The method of claim 14, wherein linearlyadvancing the spacer creates a gap between the inferior and superiorsurfaces of the upper and lower bodies.
 17. The method of claim 14,wherein a leading end of the spacer comprises a wedge shaped nose. 18.The method of claim 17, wherein at least one of the upper and lowerbodies comprise a ramped surface that is engaged by the wedge shapednose as the spacer is linearly advanced.
 19. The method of claim 14,further comprising providing an other elongated insertion instrument,wherein the elongated insertion instruments are located on oppositesides of the spacer during use.
 20. The method of claim 19, wherein theelongated insertion instruments each comprise longitudinal axis runningalong their length, and wherein the longitudinal axes of the elongatedinsertion instruments are arranged substantially parallel to one anotherduring use.
 21. The method of claim 20, further comprising linearlyadvancing the spacer between the elongated insertion instruments in adirection substantially parallel to longitudinal axes of the elongatedinsertion instruments.
 22. The method of claim 14, wherein an interfacebetween the elongated insertion instrument and the spacer comprises achannel and complementary protrusion that guides linear advancement ofthe spacer.
 23. The method of claim 22, wherein the spacer comprises aprotrusion that engages a complementary channel of the elongatedinsertion instrument, and wherein the complementary channel is formed inthe surface of the elongated instrument and extends along at least amajority of a longitudinal length of the elongated insertion instrument.24. The method of claim 14, further comprising moving an other elongatedinsertion instrument linearly to advance the spacer linearly during use.25. The method of claim 24, wherein the other elongated insertioninstrument engages a trailing end of the spacer and is moved linearly topush the spacer linearly.
 26. The method of claim 14, wherein at leastone of the upper or lower body comprises an instrument engagementfeature engaged by a complementary body engagement feature of theelongated insertion instrument to rigidly couple the elongated insertioninstrument to the upper or lower body during use.
 27. The method ofclaim 14, wherein releasably coupling the elongated insertion instrumentto at least one of the upper body and the lower body comprisesreleasably coupling the elongated insertion instrument to the upper bodyand the lower body.
 28. An intervertebral implant system for a humanspine, comprising: an upper body configured to be disposed in anintervertebral space between an upper vertebra and a lower vertebraduring use, wherein the upper body comprises: a superior surfaceconfigured to be disposed adjacent the upper vertebra, and an inferiorsurface opposite the superior surface; a lower body configured to bedisposed into the intervertebral space between the upper vertebra andthe lower vertebra during use, wherein the lower body comprises: aninferior surface configured to be disposed adjacent the lower vertebra,and a superior surface opposite the inferior surface; an elongatedinsertion instrument configured to be releasably coupled to at least oneof the upper body and the lower body during use; and a spacer configuredto be linearly advanced between the inferior surface of the upper bodyand the superior surface of the lower body during use; an otherelongated insertion instrument, wherein the elongated insertioninstruments are located on opposite sides of the spacer during use,wherein the elongated insertion instruments each comprise longitudinalaxis running along their length, and wherein the longitudinal axes ofthe elongated insertion instruments are arranged substantially parallelto one another during use, wherein the spacer is advanced linearlybetween the elongated insertion instruments in a direction substantiallyparallel to longitudinal axes of the elongated insertion instrumentsfrom a substantially proximal end of the elongated insertion instrumentsto a substantially distal end of the elongated insertion instruments,wherein the elongated insertion instrument guides at least a portion oflinear advancement of the spacer, and wherein linear advancement of thespacer results in expansion of the intervertebral implant such that thesuperior surface of the upper body and the inferior surface of the lowerbody move away from one another to expand a height of the implant. 29.The system of claim 28, wherein the spacer is disposed in a gap betweenthe inferior and superior surfaces of the upper and lower bodies,respectively, during use.
 30. The system of claim 28, wherein a leadingend of the spacer comprises a wedge shaped nose.
 31. The system of claim30, wherein at least one of the upper or lower bodies comprise a rampedsurface engaged by the wedge shaped nose as the spacer is linearlyadvanced during use.
 32. The system of claim 28, wherein an interfacebetween the elongated insertion instrument and the spacer comprises achannel and complementary protrusion that guides linear advancement ofthe spacer.
 33. The system of claim 32, wherein the spacer comprises aprotrusion that engages a complementary channel of the elongatedinsertion instrument, and wherein the complementary channel is formed inthe surface of the elongated instrument and extends along at least amajority of a longitudinal length of the elongated insertion instrument.34. The system of claim 28, further comprising an other elongatedinsertion instrument, wherein the other elongated insertion instrumentis moved linearly to advance the spacer linearly during use.
 35. Thesystem of claim 34, wherein the other elongated insertion instrumentengages a trailing end of the spacer and is moved linearly to push thespacer linearly during use.
 36. The system of claim 28, wherein at leastone of the upper or lower body comprises an instrument engagementfeature engaged by a complementary body engagement feature of theelongated insertion instrument to rigidly couple the elongated insertioninstrument to the upper or lower body during use.
 37. The system ofclaim 28, wherein the elongated insertion instrument is configured to bereleasably coupled to the upper body and the lower body during use.